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Validation 7.7 VALIDATION WITH REGULAR EXPRESSIONS One of ASP.NET’s most powerful validation controls is the RegularExpressionValidator, which validates text by determining whether it matches a specific pattern. For example, e-mail addresses, phone numbers, and file names are all examples of text that has specific constraints. A phone number must be a set number of digits, an e-mail address must include exactly one @ character (with text on either side), and a file name can’t include certain special characters such as \ and ?. One way to define patterns like these is with regular expressions. Character Description * Zero or more occurrences of the previous character or
subexpression. For example, 7*8 matches 7778 or just 8. + One or more occurrences of the previous character or
subexpression. For example, 7+8 matches 7778 but not 8. ( ) Groups a subexpression that will be treated as a single
element. For example, (78)+ matches 78 and 787878. {m,n} The previous character (or subexpression) can occur from
m to n times. For example, A{1,3} matches A, AA, or
AAA. | Either of two matches. For example, 8|6 matches 8 or 6 [ ] Matches one character in a range of valid characters. For
example, [A -C] matches A, B, or C. [^] Matches one character in a range of valid characters. For
example, [A -C] matches A, B, or C. . Any character except a newline. For example, .here
matches where and there. \s Any whitespace character (such as a tab or space). \S Any nonwhitespace character \d Any digit character \D Any character that isn’t a digit. \w Any “word” character (letter, number, or underscore). \W Any character that isn’t a “word” character (letter,
number, or underscore). Table 7.4: Common (and useful) regular expressions. (Ref: Beginning ASP.NET in C# by Matthew MacDonald) munotes.in

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108 .Net technology Commonly Used Regular Expressions Content Regular Expression Description E-mail address* \S+@ \S+\.\S+ Check for an at (@) sign and dot
(.) and allow nonwhitespace
characters only. Password \w+ Any sequence of one or more
word characters (letter, space, or
underscore). Specific -length
password \w{4,10} A password that must be at least
four characters long but no
longer than ten characters. Advanced
password [a-zA-Z]\w{3,9} As with the specific -length
password, this regular
expression will allow four to ten
total characters. The twist is that
the first character must fall in
the range of a –z or A –Z Another
advanced
password [a-zA-Z]\w*\d+\w* This password starts with a letter
character, followed by zero or
more word characters, one or
more digits, and then zero or
more word characters Limited -length
field \S{4,10} Like the password example, this
allows four to ten characters, but
it allows special characters US Social
Security number \d{3} -\d{2} -\d{4} A sequence of three, two, and
then four digits, with each group
separated by a dash. You could
use a similar pattern when
requiring a phone number . Table 7.5: Commonly Used Regular Expressions (Ref: Beginning ASP.NET in C# by Matthew MacDonald) munotes.in

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Validation Example :
Figure 7.2: A sample customer form (Ref: Beginning ASP.NET in C# by Matthew MacDonald) Several types of validation are taking place on the customer form: Three RequiredFieldValidator controls make sure the user enters a username, a password, and a password confirmation. A CompareValidator ensures that the two versions of the masked password match. A RegularExpressionValidator checks that the e-mail address contains an at (@) symbol. A RangeValidator ensures the age is a number from 0 to 120. A CustomValidator performs a special validation on the server of a “referrer code.” This code verifies that the first three characters make up a number that is divisible by 7. The tags for the validator controls are as follows: munotes.in

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110 .Net technology ErrorMessage="Your password does not match." ControlToCompare="txtPassword" ControlToValidate="txtRetype" /> The form provides two validation buttons—one that requires validation and one that allows the user to cancel the task gracefully: Here’s the event-handling code for the buttons: protected void cmdSubmit_Click(Object sender, EventArgs e) { if (Page.IsValid) { lblMessage.Text = "This is a valid form."; } munotes.in

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Validation } protected void cmdCancel_Click(Object sender, EventArgs e) { lblMessage.Text = "No attempt was made to validate this form."; } The only form-level code that is required for validation is the custom validation code. The validation takes place in the event handler for the CustomValidator.ServerValidate event. protected void vldCode_ServerValidate(Object source, ServerValidateEventArgs e) { try { // Check whether the first three digits are divisible by seven. int val = Int32.Parse(e.Value.Substring(0, 3)); if (val % 7 == 0) { e.IsValid = true; } else { e.IsValid = false; } } catch { // An error occurred in the conversion. // The value is not valid. e.IsValid = false; } } munotes.in

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112 .Net technology 7.8 SUMMARY In this chapter, you learned how to use one of ASP.NET’s most practical features: validation. You saw how ASP. NET combines server-side and client-side validation to ensure bulletproof security without sacrificing the usability of your web pages. You also looked at the types of validation provided by the various validation controls, and even brushed up on the powerful pattern-matching syntax used for regular expressions 7.9 REFERANCE • Beginning ASP.NET in C# by Matthew MacDonald 7.10 QUESTIONS 1. Write and explain Validation control. 2. Explain Server-side validation 3. Explain Client-side validation 4. Explain Manual validation 5. Explain validation with Regular expression.  munotes.in

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113 8 RICH CONTROLS Unit Structure : 8.0 Objectives 8.1 Introduction 8.2 Calendar Control 8.2.1 Formatting the Calendar 8.2.2 CalendarDay Properties 8.3 AdRotator Control 8.3.1 The Advertisement File 8.3.2 The AdRotator Class 8.4 MultiView Control 8.4.1 Creating Views 8.5 Summary 8.6 Reference 8.7 Questions 8.0 OBJECTIVES  Rich controls are web controls that model complex user interface elements.  Although no strict definition exists for what is and what isn’t a rich control, the term commonly describes a web control that has an object model that’s distinctly separate from the HTML it generates. 8.1 INTRODUCTION  Rich control provides object model that has complex HTML representation and also client-side JavaScript  Rich controls are web controls that model complex user interface elements.  A typical rich control can be programmed as a single object but renders itself using a complex sequence of HTML elements.  Rich controls can also react to user actions (such as a mouse click on a specific region of the control) and raise more-meaningful events that your code can respond to on the web server.  In other words, rich controls give you a way to create advanced user interfaces in your web pages without writing lines of convoluted HTML. munotes.in

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114 .Net technology 8.2 CALENDAR CONTROL  The Calendar control presents a miniature calendar that you can place in any web page.  The Calendar control presents a single-month view  The user can navigate from month to month by using the navigational arrows, at which point the page is posted back and ASP.NET automatically provides a new page with the correct month values
Figure 8.1: The default Calendar (Ref: Beginning ASP.NET in C# by Matthew MacDonald)  Depending on the value you choose, you can allow users to select days (Day), entire weeks (DayWeek), whole months (DayWeekMonth), or render the control as a static calendar that doesn’t allow selection (None).  You may also want to set the Calendar.FirstDayOfWeek property to configure how a week is shown.  For example, set FirstDayOfWeek to the enumerated value Sunday, and weeks will be selected from Sunday to Saturday.  The following code demonstrates this technique: lblDates.Text = "You selected these dates:
"; foreach (DateTime dt in MyCalendar.SelectedDates) { lblDates.Text += dt.ToLongDateString() + "
"; }
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Rich Controls
Figure 8.2: Selecting multiple dates (Ref: Beginning ASP.NET in C# by Matthew MacDonald) 8.2.1 Formatting the Calendar  The Calendar control provides a whole host of formatting-related properties. Member Description DayHeaderStyle The style for the section of the Calendar that
displays the days of the week (as column
headers). DayStyle The default style for the dates in the current
month NextPrevStyle The style for the navigation controls in the title
section that move from month to month. OtherMonthDayStyle The style for the dates that aren’t in the
currently displayed month. These dates are
used to “fill in” the calendar grid. For
example, the first few cells in the topmost row
may display the last few days from the
previous month.
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116 .Net technology Member Description SelectedDayStyle The style for the selected dates on the calendar SelectorStyle The style for the week and month date
selection contro ls. TitleStyle The style for the title section. TodayDayStyle The style for the date designated as today
(represented by the TodaysDate property of
the Calendar control). WeekendDayStyle The style for dates that fall on the weekend. Table 8.1: Properties for Calendar Styles (Ref: Beginning ASP.NET in C# by Matthew MacDonald)  You can adjust each style by using the Properties window.  For a quick shortcut, you can set an entire related color scheme by using the Calendar’s Auto Format feature.  To do so, start by selecting the Calendar on the design surface of a web form. Then click the arrow icon that appears next to its top-right corner to show the Calendar’s smart tag, and click the Auto Format link.  You’ll be presented with a list of predefined formats that set the style properties
Figure 8.3: Calendar Styles (Ref: Beginning ASP.NET in C# by Matthew MacDonald)
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Rich Controls 8.2.2 CalendarDay Properties Property Description Date The DateTime object that represents this date. IsWeekend True if this date falls on a Saturday or Sunday. IsToday True if this value matches the
Calendar.TodaysDate property, which is set to the
current day by default. IsOtherMonth True if this date doesn’t belong to the current
month but is displaye d to fill in the first or last row. IsSelectable Allows you to configure whether the user can
select this day. Table 8.2: CalendarDay Properties (Ref: Beginning ASP.NET in C# by Matthew MacDonald) Members of the Calendar control class. Member Description Caption and
CaptionAlign Gives you an easy way to add a title to the
calendar. By default, the caption appears at the
top of the title area, just above the month
heading. CellPadding ASP.NET creates a date in a separate cell of an
invisible t able. CellPadding is the space, in
pixels, between the border of each cell and its
contents. CellSpacing The space, in pixels, between cells in the same
table. DayNameFormat Determines how days are displayed in the
calendar header. Valid values are Full (as in
Sunday), FirstLetter (S), FirstTwoLetters (Su),
and Short (Sun), which is the default. FirstDayOfWeek Determines which day is displayed in the first
column of the calendar. The values are any day
name from the FirstDayOfWeek enumeration
(such as Sunday). By default, this is Sunday. TitleFormat Configures how the month is displayed in the
title area. Valid values include Month and
MonthYear TodaysDate Sets which day should be recognized as the
current date and formatted with the
TodayDayStyle. This defaults to the current day
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118 .Net technology Member Description VisibleDate Gets or sets the date that specifies what month
will be displayed in the calendar. This allows
you to change the calendar display without
modifying the current date selection. ShowDayHeader ,
ShowGridLines,
ShowNextPrevMonth,
and ShowTitle These Boolean properties allow you to configure
whether various parts of the calendar are shown,
including the day titles, gridlines between every
day, the previous/next month navigation links,
and the titl e section. Note that hiding the title
section also hides the next and previous month
navigation controls. Table 8.3: Calendar Members (Ref: Beginning ASP.NET in C# by Matthew MacDonald) 8.3 ADROTATOR CONTROL  The basic purpose of the AdRotator is to provide a graphic on a page that is chosen randomly from a group of possible images.  In other words, every time the page is requested, an image is selected at random and displayed, which is the rotation indicated by the name AdRotator.  One use of the AdRotator is to show banner-style advertisements on a page, but you can use it anytime you want to vary an image randomly. 8.3.1 The Advertisement File  The AdRotator stores its list of image files in an XML file. This file uses the format shown here: prosetech.jpg http://www.prosetech.com ProseTech Site 1 Computer  This example shows a single possible advertisement, which the AdRotator control picks at random from the list of advertisements. munotes.in

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Rich Controls  To add more advertisements, you would create multiple elements and place them all inside the root element:  Each element has a number of other important properties that configure the link, the image, and the frequency. Element Description ImageUrl The image that will be displayed. This can be a relative
link (a file in the current directory) or a fully qualified
Internet URL. NavigateUrl The link that will be followed if the user clicks the
banner. This can be a relative or fully qualified URL. AlternateText The text that will be displayed instead of the picture if it
cannot be displayed. This text will also be used as a
tooltip in some newer browsers. Impressions A number that sets how often an advertisement will
appear. This number is relative to the numbers specified
for other ads. For example, a banner with the value 10
will be shown twice as often (on average) as the banner
with the value 5. Keyword A keyword that identifies a group of advertisements.
You can use this for filtering. For exa mple, you could
create ten advertisements and give half of them the
keyword Retail and the other half the keyword
Computer. Table 8.4: Advertisement File Elements (Ref: Beginning ASP.NET in C# by Matthew MacDonald) 8.3.2 The AdRotator Class  The actual AdRotator class provides a limited set of properties.  You specify both the appropriate advertisement file in the AdvertisementFile property and the type of window that the link should follow (the Target window). The target can name a specific frame munotes.in

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120 .Net technology Target Description _blank The link opens a new unframed window. _parent The link opens in the parent of the current frame. _self The link opens in the current frame. _top The link opens in the topmost frame of the current
window Table 8.5: Advertisement File Elements (Ref: Beginning ASP.NET in C# by Matthew MacDonald)  Optionally, you can set the KeywordFilter property so that the banner will be chosen from a specific keyword group. This is a fully configured AdRotator tag:  The event-handling code for this example simply configures a HyperLink control named lnkBanner based on the randomly selected advertisement: protected void Ads_AdCreated(Object sender, AdCreatedEventArgs e) { // Synchronize the Hyperlink control. lnkBanner.NavigateUrl = e.NavigateUrl; // Syncrhonize the text of the link. lnkBanner.Text = “Click here for information about our sponsor: “; lnkBanner.Text += e.AlternateText; } 8.4 MULTIVIEW CONTROL  The MultiView is the simpler of the two multiple-view controls.  The MultiView gives you a way to declare multiple views and show only one at a time.  Creating a MultiView is suitably straightforward. You add the tag to your .aspx page file and then add one tag inside it for each separate view: ... ... ... munotes.in

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Rich Controls 8.4.1 Creating Views  Full markup for a MultiView that splits the greeting card controls into three views named View1, View2, and View3: Choose a foreground (text) color:


Choose a background color:
Choose a border style:

Choose a font name:


Specify a font size:


Enter the greeting text below:
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Figure 8.4: Designing multiple views (Ref: Beginning ASP.NET in C# by Matthew MacDonald) 8.4.2 Showing a View  If you run this example, you won’t see what you expect.  The MultiView will appear empty on the page, and all the controls in all your views will be hidden.  The reason this happens is that the MultiView.ActiveViewIndex property is, by default, set to –1. The ActiveViewIndex property determines which view will be shown.  If you set the ActiveViewIndex to 0, however, you’ll see the first view. Similarly, you can set it to 1 to show the second view, and so on.  You can set this property by using the Properties window or using code: // Show the first view. MultiView1.ActiveViewIndex = 0;  This example shows the first view (View1) and hides whatever view is currently being displayed, if any.
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Rich Controls  You can also use the SetActiveView() method, which accepts any one of the view objects you’ve created, rather than the view name. MultiView1.SetActiveView(View1);  Following table shows lists all the recognized command names. Each command name also has a corresponding static field in the MultiView class. Command Name MultiView Field Description PrevView PreviousViewCommandName Moves to the
previous view. NextView NextViewCommandName Moves to the next
view. SwitchViewByID SwitchViewByIDCommandNam
e Moves to the view
with a specific ID
(string name). The
ID is taken from
the
CommandArgum
ent property of the
button control. SwitchViewByInd
ex SwitchViewByIndexCommandN
ame Moves to the view
with a specific
numeric index.
The index is taken
from the
CommandArgum
ent property of the
button control. Table 8.6: Recognized Command Names for the MultiView (Ref: Beginning ASP.NET in C# by Matthew MacDonald) 8.5 SUMMARY  This chapter showed you how the rich Calendar, AdRotator, MultiView, and Wizard controls can go far beyond the limitations of ordinary HTML elements.  When you’re working with these controls, you don’t need to think about HTML at all. Instead, you can focus on the object model that’s defined by the control. munotes.in

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124 .Net technology 8.6 REFERENCE • Beginning ASP.NET in C# by Matthew MacDonald 8.7 QUESTIONS 1. Explain Calendar control. 2. Write and explain formatting properties for calendar. 3. Write and explain members of the calender control. 4. Explain AdRotator control. 5. Explain multiview control.  munotes.in

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Themes and Master Pages 9 THEMES AND MASTER PAGES Unit Structure: 9.0 Objectives 9.1 Introduction 9.2 How Themes Work 9.3 Applying a Simple Theme 9.4 Handling Theme Conflicts 9.5 Simple Master Page and Content Page 9.6 Connecting Master pages and Content Pages 9.7 Master Page with Multiple Content Regions 9.8 Master Pages and Relative Paths 9.9 Summary 9.10 Reference 9.11 Questions 9.0 OBJECTIVES Using the techniques, you’ve learned so far, you can create polished web pages and let users surf from one page to another. However, to integrate your web pages into a unified, consistent website, you need a few more tools. In this chapter, you’ll consider three of the most important tools that you can use: styles, themes, and master pages. 9.1 INTRODUCTION ASP. NET includes themes feature, which plays a similar role as styles but works exclusively with server controls. Best feature for standardizing websites is master pages. Essentially, a master page is a blueprint for part of your website. Using a master page, you can define web page layout, complete with the usual details such as headers, menu bars, and ad banners. Once you’ve perfected a master page, you can use it to create content pages. Each content page automatically acquires the layout and the content of the linked master page. By using themes, and master pages, you can ensure that all the pages on your website share a standardized look and layout. munotes.in

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126 .Net technology 9.2 HOW THEMES WORK All themes are application specific. To use a theme in a web application, you need to create a folder that defines it. This folder needs to be placed in the App_Themes folder, which must be placed inside the top-level directory for your web application. To use theme, you need to create at least one skin file in the theme folder. A skin file is a text file with the .skin extension
Figure 9.1: Themes and skins (Ref: Beginning ASP.NET in C# by Matthew MacDonald) 9.3 APPLYING A SIMPLE THEME: To add a theme to your project, select Website➤ Add New Item, and choose Skin File. Visual Studio will warn you that skin files need to be placed in a subfolder of the App_Themes folder and ask you whether that’s what you intended. If you choose Yes, Visual Studio will create a folder with the same name as your theme file. You can then rename the folder and the file to whatever you’d like to use.
Figure 9.2: A theme in the Solution Explorer (Ref: Beginning ASP.NET in C# by Matthew MacDonald)
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Themes and Master Pages Here’s a sample skin file that sets background and foreground colors for several common controls: To apply the theme in a web page, you need to set the Theme attribute of the Page directive to the folder name for your theme. <%@ Page Language="C#" AutoEventWireup ="true" ... Theme="FunkyTheme" %>
Figure 9.3: A simple page after theming (Ref: Beginning ASP.NET in C# by Matthew MacDonald) 9.4 HANDLING THEME CONFLICTS: When properties conflict between your controls and your theme, the theme wins. However, in some cases you might want to change this behavior so that your controls can fine-tune a theme by specifically overriding certain details. ASP.NET gives you this option, but it’s an all-or-nothing setting that applies to all the controls on the entire page. To make this change, just use the StyleSheetTheme attribute instead of the Theme attribute in the Page directive. <%@ Page Language="C#" AutoEventWireup ="true" ... StyleSheetTheme="FunkyTheme" %>
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128 .Net technology Now the custom yellow background of the ListBox control takes precedence over the background color specified by the theme. Figure shows the result—and a potential problem. Because the foreground color has been changed to white, the lettering in the large text box is now impossible to see. Overlapping formatting specifications can cause glitches like this, which is why it’s often better to let your themes take complete control by using the Theme attribute.
Figure 9.4: Giving the control tag precedence over the theme (Ref: Beginning ASP.NET in C# by Matthew MacDonald) 9.5 SIMPLE MASTER PAGE AND CONTENT PAGE: Master pages are similar to ordinary ASP.NET pages. Like ordinary pages, master pages are text files that can contain HTML, web controls, and code. However, master pages have a different file extension (.master instead of .aspx), and they can’t be viewed directly by a browser. Instead, master pages must be used by other pages, which are known as content pages. Essentially, the master page defines the page structure and the common ingredients. A single master page might define the layout for the entire site. Every page would use that master page, and as a result, every page would have the same basic organization and the same title, footer, and so on.
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Themes and Master Pages However, each page would also insert its specific information, such as product descriptions, book reviews, or search results, into this template To create a master page in Visual Studio, select Website➤Add New Item from the menu. Select Master Page, give it a file name (such as SiteTemplate.master, used in the next example), and click Add. The ContentPlaceHolder is the portion of the master page that a content page can change. Or, to look at it another way, everything else that’s set in the master page is unchangeable in a content page. If you add a header, that header appears in every content page. If you want to give the content page the opportunity to supply content in a specific section of the page, you need to add a ContentPlaceHolder.
Figure 9.5: A new master page (Ref: Beginning ASP.NET in C# by Matthew MacDonald) When you first create a master page, you’ll start with two ContentPlaceHolder controls. One is defined in thesection, which gives content pages the add page metadata, such as search keywords and style sheet links. The second, more important ContentPlaceHolder is defined in the section, and represents the displayed content of the page. It appears on the page as a faintly outlined box. If you click inside it or hover over it, the name of ContentPlaceHolder appears in a tooltip.
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130 .Net technology Now you’re ready to create a content page based on this master page. To take this step, select Website➤ Add New Item from the menu. Select Web Form, and choose to select a master page. Click Add. When you’re prompted to choose a master page, use the one you created with the header and footer.
Figure 9.6: Creating a content page (Ref: Beginning ASP.NET in C# by Matthew MacDonald) Your content page will have all the elements of the master page 9.6 CONNECTING MASTER PAGES AND CONTENT PAGES: When you create a master page, you’re building something that looks much like an ordinary ASP.NET web form. The key difference is that, although web forms start with the Page directive, a master page starts with a Master directive that specifies the same information. Here’s the Master directive for the simple master page shown in the previous example: <%@ Master Language="C#" AutoEventWireup ="true" CodeFile="SiteTemplate.master.cs" Inherits="SiteTemplate" %> The ContentPlaceHolder is less interesting. You declare it like any ordinary control. Here’s the complete code for the simple master page: <%@ Master Language="C#" AutoEventWireup ="true" CodeFile="SiteTemplate.master.cs" Inherits="SiteTemplate" %>
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Themes and Master Pages

This is a simple footer.

When you create a content page, ASP.NET links your page to the master page by adding an attribute to the Page directive. This attribute, named MasterPageFile, indicates the associated master page. Here’s what it looks like: <%@ Page Language="C#" MasterPageFile ="~/SiteTemplate.master" AutoEventWireup="true" CodeFile="SimpleContentPage.aspx.cs" Inherits="SimpleContentPage" Title="Untitled Page" %> Notice that the MasterPageFile attribute begins with the path ~/ to specify the root website folder. 9.7 MASTER PAGE WITH MULTIPLE CONTENT REGIONS Master pages aren’t limited to one ContentPlaceHolder. Instead, you can insert as many as you need to give the client the ability to intersperse content in various places. All you need to do is add multiple ContentPlaceHolder controls and arrange them appropriately. Example: <%@ Master Language="C#" AutoEventWireup ="true" CodeFile="MultipleContent.master.cs" Inherits="MultipleContent" %> munotes.in

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OTHER LINKS

This is a simple footer.

When you create a new content page based on this master page, Visual Studio will start you with one Content control for each ContentPlaceHolder in the master page, making your life easy. All you need to do is insert the appropriate information. Here’s a slightly shortened example, with some of the text replaced with an ellipsis (. . .) to save space: <%@ Page Language="C#" MasterPageFile ="~/MultipleContent.master" AutoEventWireup="true" CodeFile="MultipleContentPage.aspx.cs" Inherits="MultipleContentPage" Title="Content Page" %> This is the generic content for this page. Here you might provide some site specific text ... Here’s alink.
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Themes and Master Pages 9.8 MASTER PAGES AND RELATIVE PATHS: One quirk that can catch unsuspecting developers is the way that master pages handle relative paths. If all you’re using is static text, this issue won’t affect you. However, if you addError! Filename not specified.tags or any other HTML tag that points to another resource, problems can occur. The problem shows up if you place the master page in a different directory from the content page that uses it. This is a recommended best practice for large websites. In fact, Microsoft encourages you to use a dedicated folder for storing all your master pages. However, if you’re not suitably careful, this can cause problems when you use relative paths. For example, imagine you put a master page in a subfolder named MasterPages and add the followingError! Filename not specified.tag to the master page: Assuming the file \MasterPages\banner.jpg exists, this appears to work fine. The image will even appear in the Visual Studio design environment. However, if you create a content page in another subfolder, the image path is interpreted relative to that folder. If the file doesn’t exist there, you’ll get a broken link instead of your graphic. Even worse, you could conceivably get the wrong graphic if another image has the same file name. To solve your problem, you could try to think ahead and write your URL relative to the content page where you want to use it. But this creates confusion and limits where your master page can be used. A better fix is to turn yourError! Filename not specified.tag into a server-side control, in which case ASP.NET will fix the mistake: 9.9 SUMMARY Building a professional web application involves much more than designing individual web pages. You also need the tools to integrate munotes.in

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134 .Net technology your web pages in a complete, unified website. In this chapter, you considered best ways to do exactly that. ASP.NET themes feature, which lets you effortlessly apply a group of property settings to a control. Finally, you learned to use master pages, which allow you to standardize the layout of your website. All these features make it easy to bring your pages together into a well-integrated, consistent web application. 9.10 REFERANCE • Beginning ASP.NET in C# by Matthew MacDonald 9.11 QUESTIONS 1. Explain themes and master pages in detail. 2. What is concept of master pages and content pages and how connect them? 3. Explain how themes works. 4. Explain how to handle theme conflicts.  munotes.in

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Website Navigation 10 WEBSITE NAVIGATION Unit Structure : 10.0 Objectives 10.1 Introduction 10.2 Site Maps 10.3 URL Mapping and Routing 10.4 SiteMapPath Control 10.5 TreeView Control 10.6 Menu Control 10.7 Summary 10.8 Reference 10.9 Questions 10.0 OBJECTIVES  Website navigation is an essential part of web design because it contributes to the user experience.  Understanding website navigation can help you allow users to access the information they want as quickly as possible by presenting an enjoyable, intuitive layout while increasing ease of use. 10.1 INTRODUCTION  ASP.NET provides various site-navigation features which gives a consistent way for visitors to navigate the site.  These features are Site Maps. URL Mapping and Routing, SiteMapPath. 10.2 SITE MAPS  If your website has more than a handful of pages, you’ll probably want some sort of navigation system to let users move from one page to the next.  As with all the best ASP.NET features, ASP.NET navigation is flexible, configurable, and pluggable. It consists of three components: 1. A way to define the navigation structure of your website. This part is the XML site map, which is (by default) stored in a file. munotes.in

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136 .Net technology 2. A convenient way to read the information in the site map file and convert it to an object model. The SiteMapDataSource control and the XmlSiteMapProvider perform this part. 3. A way to use the site map information to display the user’s current position and give the user the ability to easily move from one place to another. This part takes place through the navigation controls you bind to the SiteMapDataSource control, which can include breadcrumb links, lists, menus, and trees.
Figure 10.1: ASP.NET navigation with site maps (Ref: Beginning ASP.NET in C# by Matthew MacDonald)  You can create a site map by using a text editor such as Notepad, or you can create it in Visual Studio by choosing Website ➤ Add New Item and then choosing the Site Map option.  Either way, it’s up to you to enter all the site map information by hand.  The only difference is that if you create it in Visual Studio, the site map will start with a basic structure that consists of three siteMap nodes. Rule 1: Site Maps Begin with the Element • Every Web.sitemap file begins by declaring the element and ends by closing that element. You place the actual site map information between the start and end tags (where the three dots are shown here): ... • The xmlns attribute is required, and must be entered exactly as shown here. This tells ASP.NET that the XML file uses the ASP.NET site map standard.
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Website Navigation Rule 2: Each Page Is Represented by a Element • Essentially, every site map defines an organization of web pages. • To insert a page into the site map, you add the element with some basic information. • Namely, you need to supply the title of the page, a description and the URL. • You add these three pieces of information by using three attributes—named title, description, and url, as shown here: • Notice that this element ends with the characters />. • This indicates it’s an empty element that represents a start tag and an end tag in one. • Empty elements never contain other nodes. • Here’s a complete, valid site map file that uses this page to define a website with exactly one page: Rule 3: A Element Can Contain Other Elements • Site maps don’t consist of simple lists of pages. Instead, they divide pages into groups. • To represent this in a site map file, you place one inside another. • Instead of using the empty element syntax shown previously, you’ll need to split your element into a start tag and an end tag: ... • Now you can slip more nodes inside. Here’s an example of a Home group that contains two more pages:

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Figure 10.2: Three nodes in a site map (Ref: Beginning ASP.NET in C# by Matthew MacDonald) • In this case, all three nodes are links. This means the user could surf to one of three pages. • However, when you start to create more-complex groups and subgroups, you might want to create nodes that serve only to organize other nodes but aren’t links themselves. • In this case, just omit the url attribute, as shown here with the Products node: Rule 4: Every Site Map Begins with a Single • Another rule applies to all site maps. • A site map must always have a single root node.
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Website Navigation • All the other nodes must be contained inside this root-level node. • That means the following is not a valid site map, because it contains two top-level nodes: • The following site map is valid, because it has a single top-level node (Home), which contains two more nodes: Rule 5: Duplicate URLs Are Not Allowed • You cannot create two site map nodes with the same URL. • This might seem to present a bit of a problem when you want to have the same link in more than one place—and it does. • However, it’s a requirement because the default SiteMapProvider included with ASP.NET stores nodes in a collection, with each item indexed by its unique URL. • This limitation doesn’t prevent you from creating more than one URL with minor differences pointing to the same page. For example, consider the following portion of a site map. • These two nodes are acceptable, even though they lead to the same page (products.aspx), because the two URLs have different query string arguments at the end. munotes.in

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140 .Net technology 10.3 URL MAPPING AND ROUTING URL Mapping  In some situations, you might want to have several URLs lead to the same page.  This might be the case for a number of reasons—maybe you want to implement your logic in one page and use query string arguments but still provide shorter and easier-to-remember URLs to your website users.  The basic idea behind ASP.NET URL mapping is that you map a request URL to a different URL.  The mapping rules are stored in the web.config file, and they’re applied before any other processing takes place.  Of course, for ASP.NET to apply the remapping, it must be processing the request, which means the request URL must use a file type extension that’s mapped to ASP.NET.  We can define URL mapping in the section of the web.config file. You supply two pieces of information—the request URL (as the url attribute) and the new destination URL (mappedUrl). Here’s an example: ...  In order for ASP.NET to make a match, the URL that the browser submits must match the URL specified in the web.config file almost exactly.  When you use URL mapping, the redirection takes place in the same way as the Server.Transfer() method, which means no round-trip happens and the URL in the browser will still show the original request URL, not the new page. munotes.in

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Website Navigation URL ROUTING  URL routing was originally designed as a core part of ASP.NET MVC, an alternative framework for building web pages.  Unlike URL mapping, URL routing doesn’t take place in the web.config file. Instead, it’s implemented using code.  Typically, you’ll use the Application_Start() method in the global.asax file to register all the routes for your application.  To register a route, you use the RouteTable class from the System.Web.Routing namespace. To make life easier, you can start by importing that namespace: using System.Web.Routing;  The RouteTable class provides a static property named Routes, which holds a collection of Route objects that are defined for your application.  Initially, this collection is empty, but you can create custom routes by calling the MapPageRoute() method, which takes three arguments: • routeName: This is a name that uniquely identifies the route. It can be whatever you want. • routeUrl: This specifies the URL format that browsers will use. Typically, a route URL consists of one or more pieces of variable information, separated by slashes, which are extracted and provided to your code. For example, you might request a product page by using a URL such as /products/4312. • physicalFile: This is the target web form—the place where users will be redirected when they use the route. The information from the original routeUrl will be parsed and made available to this page as a collection through the Page.RouteData property.  Here’s an example that adds two routes to a web application when it first starts: protected void Application_Start(object sender, EventArgs e) { RouteTable.Routes.MapPageRoute("product-details", "product/{productID}", "~/productInfo.aspx"); RouteTable.Routes.MapPageRoute("products-in-category", "products/category/{categoryID}", "~/products.aspx"); } munotes.in

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142 .Net technology 10.4 SITEMAPPATH CONTROL  The TreeView shows the available pages, but it doesn’t indicate where you’re currently positioned. To solve this problem, it’s common to use the TreeView in conjunction with the SiteMapPath control.  The SiteMapPath provides breadcrumb navigation, which means it shows the user’s current location and allows the user to navigate up the hierarchy to a higher level by using links.  Using the SiteMapPath control, the user can return to the default.aspx page.
Figure 10.3: Breadcrumb navigation with SiteMapPath (Ref: Beginning ASP.NET in C# by Matthew MacDonald) Lists some of its most commonly configured properties. Property Description ShowToolTips Set this to false if you don’t want the
description text to appear when the user
hovers over a part of the site map path. ParentLevelsDisplayed This sets the maximum number of levels
above the current page that will be shown
at once. By defa ult, this setting is –1, which
means all levels will be shown. RenderCurrentNodeAsLink If true, the portion of the page that
indicates the current page is turned into a
clickable link. By default, this is false
because the user is already at the current
page.
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Website Navigation PathDirection You have two choices: RootToCurrent (the
default) and CurrentToRoot (which
reverses the order of levels in the path). PathSeparator This indicates the characters that will be
placed between each level in the path. The
default is the greater -than symbol (>).
Another common path separator is the
colon (:). Table 10.1: SiteMapPath Appearance-Related Properties (Ref: Beginning ASP.NET in C# by Matthew MacDonald) Using SiteMapPath Styles and Templates Style Template Applies To NodeStyle NodeTemplate All parts of the path
except the root and
current node. CurrentNodeStyle CurrentNodeTemplate The node representing
the current page. RootNodeStyle RootNodeTemplate The node representing
the root. If the root node
is the same as th e current
node, the current node
template or styles are
used. PathSeparatorStyle PathSeparatorTemplate The separator between
each node Table 10.2: SiteMapPath Styles and Templates (Ref: Beginning ASP.NET in C# by Matthew MacDonald) 10.5 TREEVIEW CONTROL  The TreeView has a slew of properties that let you change how it’s displayed on the page. One of the most important properties is ImageSet, which lets you choose a predefined set of node icons.  The TreeView offers 16 possible ImageSet values, which are represented by the TreeViewImageSet enumeration.  For example, following Figure shows the same RevoStock navigation page you considered earlier, but this time with an ImageSet value of TreeViewImageSet.Faq. munotes.in

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Figure 10.4: A TreeView with fancy node icons (Ref: Beginning ASP.NET in C# by Matthew MacDonald)  Here’s the complete TreeView markup: 10.5.1 Useful TreeView Properties Property Description MaxDataBindDepth Determines how many levels the TreeView will
show. By default, MaxDataBindDepth is –1, and
you’ll see the entire tree. ExpandDepth Lets you specify how many levels of nodes will be
visible at first. If you use 0, the TreeView begins
completely closed. NodeIndent Sets the number of pixels between each level of
nodes in the TreeView. Set this to 0 to create a
nonindented TreeView, which saves space. ImageSet Lets you use a predefined collection of node
images for collapsed, expanded, and
nonexpandable nodes. ShowLines Adds lines that connect every node when set to
true. NodeWrap Lets a node text -wrap over more than one line
when set to true. ShowCheckBoxes Shows a check box next to every node when set to
true. This isn’t terribly useful for site maps, but it
is useful with other types of trees. Table 10.3: Useful TreeView Properties (Ref: Beginning ASP.NET in C# by Matthew MacDonald)
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Website Navigation 10.5.2 TreeView Styles  Styles are represented by the TreeNodeStyle class, which derives from the more conventional Style class.  As with other rich controls, the styles give you options to set background and foreground colors, fonts, and borders. TreeNodeStyle-Added Properties Property Description ImageUrl The URL for the image shown next to the node. NodeSpacing The space (in pixels) between the current node and
the node above and below. VerticalPadding The space (in pixels) between the top and bottom
of the node text and border around the text. HorizontalPadding The space (in pixels) between the left and right of
the node text and border around the text. ChildNodesPadding The space (in pixels) between the last child node of
an expanded par ent node and the following node. Table 10.4: TreeNodeStyle-Added Properties (Ref: Beginning ASP.NET in C# by Matthew MacDonald) 10.6 MENU CONTROL  The Menu control is another rich control that supports hierarchical data. Like the TreeView, you can bind the Menu control to a data source, or you can use MenuItem objects to fill it by hand. munotes.in

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Figure 10.5: Navigating through the menu (Ref: Beginning ASP.NET in C# by Matthew MacDonald)  Overall, the Menu and TreeView controls expose strikingly similar programming models, even though they render themselves quite differently.  They also have a similar style-based formatting model. But a few noteworthy differences exist: • The Menu displays a single submenu. The TreeView can expand an arbitrary number of node branches at a time. • The Menu displays a root level of links in the page. All other items are displayed using fly-out menus that appear over any other content on the page. The TreeView shows all its items inline in the page. • The Menu supports templates. The TreeView does not. (Menu templates are discussed later in this section.) • The TreeView supports check boxes for any node. The Menu does not.
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Website Navigation • The Menu supports horizontal and vertical layouts, depending on the Orientation property. The TreeView supports only vertical layout. Menu Styles Static Style Dynamic Style Description StaticMenuStyle DynamicMenuStyle Sets the appearance of
the overall “box” in
which all the menu
items appear. In the
case of
StaticMenuStyle, this
box appears on the
page, and with
DynamicMenuStyle,
it appears as a pop -up. StaticMenuItemStyle DynamicMenuItemStyle Sets the appearance of
individual menu
items. StaticSelectedStyle DynamicSelectedStyle Sets the appearance of
the selected item.
Note that the selected
item isn’t the item
that’s currently being
hovered over; it’s the
item that was
previously clicked StaticHoverStyle DynamicHoverStyle Sets the appearance of
the item that the user
is hovering over with
the mouse. Table 10.5: Menu Styles (Ref: Beginning ASP.NET in C# by Matthew MacDonald) 10.7 SUMMARY  In this chapter, you explored the new navigation model and learned how to define site maps and bind the navigation data.  You then considered three controls that are specifically designed for navigation data: the SiteMapPath, TreeView, and Menu.  Using these controls, you can add remarkably rich site maps to your websites with very little coding. munotes.in

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148 .Net technology  But before you begin, make sure you’ve finalized the structure of your website.  Only then will you be able to create the perfect site map and choose the best ways to present the site map information in the navigation controls. 10.8 REFERANCE • Beginning ASP.NET in C# by Matthew MacDonald 10.9 QUESTIONS 1. Explain SiteMapPath control in detail. 2. Write note on menu control. 3. Write note on TreeView control. 4. Write and explain Menu style. 5. Write and explain TreeView properties.  munotes.in

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149 11 ADO.NET Unit Structure : 11.0 Objective 11.1 Introduction 11.2 Data Provider Model 11.3 Direct Data Access 11.4 Creating a Connection 11.5 Select Command 11.6 DataReader 11.7 Disconnected Data Access 11.8 Summary 11.9 Reference for further reading 11.10 Unit End Exercises 11.0 OBJECTIVE 1. To understand the basic and advanced concepts of ADO.NET. 2. To learn how to establish connection between application and data sources. 3. To study the different components of ADO.NET that are used for accessing and manipulating data are the .NET Framework data provider and the DataSet. 4. To learn how to prevent SQL injection attacks and how to use transactions. 11.1 INTRODUCTION ● ADO.NET consists of managed classes that allow .NET applications to connect to data sources (relational databases), execute commands, and manage disconnected data. ● The small miracle of ADO.NET is that it enables you to write more or less the same data access code in web applications that you write for client-server desktop applications, or even single-user applications that connect to a local database. ● This shows the implementation of the architecture of ADO.NET and the ADO.NET data providers. ● ADO.NET describes such as opening a connection, executing a SQL statement or stored procedure, and retrieving the results of a query. munotes.in

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150 .Net technology 11.2 DATA PROVIDER MODEL ● ADO.NET uses a multilayered architecture that revolves around a few key concepts, such as Connection, Command, and DataSet objects. ● One of the key differences between ADO.NET and some other database technologies is how it deals with the challenge of different data sources. ● In many past database technologies, such as classic ADO, programmers use a generic set of objects no matter what the underlying data source is. For example, if you want to retrieve a record from an Oracle database using ADO code, we use the same Connection class you would use to tackle the task with SQL Server. ● ADO.NET Data Providers A data provider is a set of ADO.NET classes that allows you to access a specific database, execute SQL commands, and retrieve data. ● A data provider is a bridge between your application and a data source. The classes that make up a data provider include the following: ○ Connection: You use this object to establish a connection to a data source. ○ Command: You use this object to execute SQL commands and stored procedures. ○ DataReader: This object provides fast read-only, forward-only access to the data retrieved from a query. ○ DataAdapter: This object performs two tasks. First, you can use it to fill a DataSet with information extracted from a data source. Second, you can use it to apply changes to a data source, according to the modifications made in a DataSet. ● ADO.NET doesn’t include generic data provider objects. Instead, it includes different data providers specifically designed for different types of data sources. Each data provider has a specific implementation of the Connection, Command, DataReader, and DataAdapter classes that’s optimized for a specific RDBMS. For example, if you need to create a connection to a SQL Server database, use a connection class named SqlConnection. ● Developers can create their own providers for proprietary data sources. In fact, numerous proof-of-concept examples are available that show how you can easily create custom ADO.NET providers to wrap non relational data stores, such as the file system or a directory service. Some third-party vendors also sell custom providers for .NET munotes.in

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ADO.Net ● The .NET Framework is bundled with a small set of four providers: ○ SQL Server provider: Provides optimized access to a SQL Server database ○ OLE DB provider: Provides access to any data source that has an OLE DB driver. ○ Oracle provider: Provides optimized access to an Oracle database ○ ODBC provider: Provides access to any data source that has an ODBC driver. Figure 1 shows the layers of the ADO.NET provider model.
Figure 1 The ADO.NET architecture 11.3 DIRECT DATA ACCESS ● ADO.NET does not provide a single set of objects that communicate with multiple database management systems (DBMSs). ● ADO.NET supports multiple data providers, each of which is optimized to interact with a specific DBMS. ● The first benefit of this approach is that you can program a specific data provider to access any unique features of a particular DBMS. ● The second benefit is that a specific data provider can connect directly to the underlying engine of the DBMS in question without an intermediate mapping layer standing between the tiers to communicate with a specific type of data source. ● Following Table 1 shows documents of some of the core common types, their base class and the key interfaces they implement.
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152 .Net technology Type of
Object Base Class Relevant
Interfaces Meaning in Life Connection DbConnection IDbConnection Provides the ability
to connect to and
disconnect from the
data store.
Connection objects
also provide access
to a related
transaction object. Command DbCommand IDbCommand Represents a SQL
query or a stored
procedure.
Command objects
also provide access
to the provider’s
data reader object. DataReader DbDataReader IDataReader,
IDataRecord Provides forward -
only, read -only
access to data using
a server -side cursor. DataAdapter DbDataAdapter
IDataAdapter,
IDbDataAdapter Transfers DataSets
between the caller
and the data store.
Data adapters
contain a connection
and a set of four
internal command
objects used to
select, insert,
update, and delete
information from
the data store. Parameter DbParameter
IDataParameter,
IDbDataParameter Represents a named
parameter within a
parameterized
query. Transaction DbTransaction IDbTransaction Encapsulates a
database transaction Table 1 Core Common Types ● Figure 2 shows the ADO.NET data providers. munotes.in

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ADO.Net ● A data provider will supply with other types beyond the objects shown in Figure 2 however, these core objects define a common baseline across all data providers.
Figure 2. ADO.NET data providers provide access to a given DBMS ADO.NET Data Providers ● A .NET Framework data provider is used for connecting to a database, executing commands, and retrieving results. ● Those results are either processed directly, placed in a DataSet in order to be exposed to the user as needed, combined with data from multiple sources, or remoted between tiers. .NET Framework data providers are lightweight, creating a minimal layer between the data source and code, increasing performance without sacrificing functionality. The following table 2 lists the data providers that are included in the .NET Framework. .NET Framework
data provider Description .NET Framework
Data Provider for
SQL Server Provides data access for Microsoft SQL Server.
Uses the System.Data.SqlClient name space. .NET Framework
Data Provider for
OLE DB For data sources exposed by using OLE DB. Uses
the System.Data.OleDb namespace.
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154 .Net technology .NET Framework
data provider Description .NET Framework
Data Provider for
ODBC For data sources exposed by using ODBC. Uses
the System.Data.Odbc namespace. .NET Framework
Data Provider for
Oracle For Oracle data sources. The .NET Framework
Data Provider for Oracle supports Oracle client
software version 8.1.7 and later, and uses the
System.Data.OracleClient namespace. EntityClient Provider Provides data access for Entity Data Model (EDM)
applications. Uses the System.Data.EntityClient
namespace. .NET Framework
Data Provider for
SQL Server Compact
4.0. Provides data access for Micro soft SQL Server
Compact 4.0. Uses the System.Data.SqlServerCe
namespace. Table 2 lists of data providers Core Objects of .NET Framework Data Providers The following table 3 outlines the four core objects that make up a .NET Framework data provider. Object Description Connection Establishes a connection to a specific data source. The base
class for all Connection objects is the DbConnection class. Command Executes a command against a data source. Exposes
Parameters and can execute in the scope of a Transaction
from a Connection. The base class for all Command objects
is the DbCommand class. DataReader Reads a forward -only, read -only stream of data from a data
source. The base class for all DataReader objects is the
DbDataReader class. DataAdapter Populates a DataSet and resolves updates with the data
source. The base class for all DataAdapter objects i s the
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ADO.Net A .NET Framework data provider also contains the classes listed in the following table 4. Object Description Transaction Enlists commands in transactions at the data
source. The base class for all Transaction
objects is the DbTransaction class. ADO.NET
also provides support for transactions using
classes in the System.Transactions namespace. CommandBuilder A helper object t hat automatically generates
command properties of a DataAdapter or
derives parameter information from a stored
procedure and populates the Parameters
collection of a Command object. The base class
for all CommandBuilder objects is the
DbCommandBuilder clas s. ConnectionStringBuilder A helper object that provides a simple way to
create and manage the contents of connection
strings used by the Connection objects. The
base class for all ConnectionStringBuilder
objects is the DbConnectionStringBuilder
class. Parameter Defines input, output, and return value
parameters for commands and stored
procedures. The base class for all Parameter
objects is the DbParameter class. Exception Returned when an error is encountered at the
data source. For an error encountered at the
client, .NET Framework data providers throw a
.NET Framework exception. The base class for
all Exception objects is the DbException class. Error Exposes the informat ion from a warning or
error returned by a data source. ClientPermission Provided for .NET Framework data provider
code access security attributes. The base class
for all ClientPermission objects is the
DBDataPermission class. Table 4 Data Providers Classes NET Framework Data Provider for SQL Server (SqlClient) ● The .NET Framework Data Provider for SQL Server (SqlClient) uses its own protocol to communicate with SQL Server. munotes.in

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156 .Net technology ● It is lightweight and performs well because it is optimized to access a SQL Server directly without adding an OLE DB or Open Database Connectivity (ODBC) layer. ● The following figure 3 shows the .NET Framework Data Provider for SQL Server with the .NET Framework Data Provider for OLE DB. ● The .NET Framework Data Provider for OLE DB communicates to an OLE DB data source through both the OLE DB Service component, which provides connection pooling and transaction services, and the OLE DB provider for the data source. Figure 3 Comparison of the .NET Framework Data Provider for SQL Server and the .NET Framework Data Provider for OLE DB ● The .NET Framework Data Provider for SQL Server classes are located in the System.Data.SqlClient namespace. ● The .NET Framework Data Provider for SQL Server supports both local and distributed transactions. For distributed transactions, the .NET Framework Data Provider for SQL Server, by default, automatically enlists in a transaction and obtains transaction details from Windows Component Services or System.Transactions. For more information, see Transactions and Concurrency. The following code example 1 shows how to include the System.Data.SqlClient namespace in your applications. using System.Data.SqlClient; Example 1 System.Data.SqlClient .NET Framework Data Provider for OLE DB ● The .NET Framework Data Provider for OLE DB (OleDb) uses native OLE DB through COM interop to enable data access. ● The .NET Framework Data Provider for OLE DB supports both local and distributed transactions. ● For distributed transactions, the .NET Framework Data Provider for OLE DB, by default, automatically enlists in a transaction and obtains transaction details from Windows Component Services. For more information, see Transactions and Concurrency.
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ADO.Net The following Table 5 shows the providers that have been tested with ADO.NET. Driver Provider SQLOLEDB Microsoft OLE DB provider for SQL Server MSDAORA Microsoft OLE DB provider for Oracle Microsoft.Jet.OLEDB.4.0 OLE DB provider for Microsoft Jet Table 5 Data Provider for OLE DB .NET Framework Data Provider for ODBC ● The .NET Framework Data Provider for ODBC (Odbc) uses the native ODBC Driver Manager (DM) to enable data access. ● The ODBC data provider supports both local and distributed transactions. For distributed transactions, the ODBC data provider, by default, automatically enlists in a transaction and obtains transaction details from Windows Component Services. The following Table 6 shows the ODBC drivers tested with ADO.NET. Driver SQL Server Microsoft ODBC for Oracle Microsoft Access Driver (*.mdb) Table 6 ODBC Drivbers .NET Framework Data Provider for Oracle ● The .NET Framework Data Provider for Oracle enables data access to Oracle data sources through Oracle client connectivity software. ● The data provider supports Oracle client software version 8.1.7 or a later version. The data provider supports both local and distributed transactions. ● The .NET Framework Data Provider for Oracle requires Oracle client software (version 8.1.7 or a later version) on the system before you can connect to an Oracle data source. ● .NET Framework Data Providers for Oracle classes are located in the System.Data.OracleClient namespace and are contained in the System.Data.OracleClient.dll assembly. You must reference both the System.Data.dll and the System.Data.OracleClient.dll when you compile an application that uses the data provider. The following code example 2 shows how to include the System.Data.OracleClient namespace in your applications. munotes.in

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158 .Net technology Example 2 System.Data.OracleClient using System.Data;
using System.Data.OracleClient; 11.4 CREATING A CONNECTION ● To connect to Microsoft SQL Server, use the SqlConnection object of the .NET Framework Data Provider for SQL Server. ● To connect to an OLE DB data source, use the OleDbConnection object of the .NET Framework Data Provider for OLE DB. ● To connect to an ODBC data source, use the OdbcConnection object of the .NET Framework Data Provider for ODBC. ● To connect to an Oracle data source, use the OracleConnection object of the .NET Framework Data Provider for Oracle. Choosing a .NET Framework Data Provider ● Depending on the design and data source for your application, .NET Framework data provider can improve the performance, capability, and integrity of your application. ● The following Table 7 discusses the advantages and limitations of each .NET Framework data provider. Table 7 .NET Framework data provider Provider Notes .NET Framework
Data Provider for
SQL Server Recommended for middle -tier applications that use
Microsoft SQL Server.
Recommended for single -tier applications that use
Microsoft Database Engine (MSDE) or SQL Server.
Recommended over use of the OLE DB provider for
SQL Server (SQLOLEDB) with the .NET Framework
Data Provider for OLE DB. .NET Framework
Data Provider for
OLE DB For SQL Server, the .NET Framework Data Provider
for SQL Server is recommended instead of this
provider.
Recommended for single -tier applications that use
Microsoft Access databases. Use of an Access
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ADO.Net Data Provider for
ODBC that use ODBC data sources. .NET Framework
Data Provider for
Oracle Recommended for middle and single -tier applications
that use Oracle data sources. 11.5 SELECT COMMAND The command object is one of the basic components of ADO .NET. 1. The Command Object uses the connection object to execute SQL queries. 2. The queries can be in the Form of Inline text, Stored Procedures or direct Table access. 3. An important feature of Command object is that it can be used to execute queries and Stored Procedures with Parameters. 4. If a select query is issued, the result set it returns is usually stored in either a DataSet or a DataReader object. The properties associated with the SqlCommand class are shown in the Table 8 below. Property Type of
Access Description Connection Read/Write The SqlConnection object that is used
by the command object to execute SQL
queries or Stored Procedure. CommandText Read/Write Represents the T -SQL Statement or the
name of the Stored Procedure. CommandType Read/Write This property indicates how the
CommandText property should be
interpreted. The possible values are:
1. Text (T -SQL Statement)
2. StoredProcedure (Stored Procedure
Name)
3. TableDirect CommandTimeout Read/Write This property indicates the time to wait
when executing a particular command.
Default Time for Execution of
Command is 30 Seconds.
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160 .Net technology Table 8 Properties of SqlCommand class ● Various Execute Methods that can be called from a Command Object. Shown in the following Table 9. Property Description ExecuteNonQuery This method executes the command specified and
returns the number of rows affected. ExecuteReader The ExecuteReader method executes the command
specified and returns an instance of SqlDataReader
class. ExecuteScalar This method executes the command specified and
returns the first column of the first row of the result
set. The remaining rows and columns are ignored. ExecuteXMLReader This method executes the command specified and
returns an instance of XmlReader class. This
method can be used to return the result set in the
form of an XML document Table 9 Properties of execute methods ExecuteNonQuery 1. The ExecuteNonQuery method is used to execute the command and return the number of rows affected. 2. The ExecuteNonQuery method cannot be used to return the result set. (Shown in example 3) Example 3 public void CallExecuteNonQuery()
{
SqlConnection conn = new SqlConnection();
conn.ConnectionString =
ConfigurationManager.ConnectionStrings["connString"].ConnectionStrin
g;
try
{
SqlCommand cmd = new SqlCommand();
cmd.Connection = conn;
cmd.CommandText = "DELETE FROM EMP WHERE DEPTNO = munotes.in

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ADO.Net 40";
cmd.CommandType = CommandType.Text;
conn.Open();
Int32 RowsAffected = cmd.ExecuteNonQuery();
MessageBox.Show(RowsAffected + " rows affected", "Message");
cmd.Dispose();
conn.Dispose();
}
catch (Exception ex)
{
MessageBox.Show(ex.Message);
}
} 11.6 DATAREADER ● A data reader provides an easy way for the programmer to read data from a database as if it were coming from a stream. ● The DataReader is the solution for forward streaming data through ADO.NET. ● The data reader is also called a firehose cursor or forward read-only cursor because it moves forward through the data. ● The data reader not only allows you to move forward through each record of the database, but it also enables you to parse the data from each column. ● The DataReader class represents a data reader in ADO.NET. ● Similar to other ADO.NET objects, each data provider has a data reader class for example; OleDbDataReader is the data reader class for OleDb data providers. Similarly, SqlDataReader and ODBC DataReader are data reader classes for SQL and ODBC data providers, respectively. ● The IDataReader interface defines the function of a data reader and works as the base class for all data provider-specific data reader classes such as OleDataReader. SqlDataReader, and OdbcDataReader. Figure 4 shows some of the classes that implement IDbDataReader. munotes.in

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Figure 4. Data Provider-specific classes implementing IdbDataReader Initializing DataReader ● call the ExecuteReader method of the Command object, which returns an instance of the DataReader. ● For example 4, use the following line of code: Example 4: SqlCommand cmd = new SqlCommand(SQL, conn);
// Call ExecuteReader to return a DataReader
SqlDataReader reader = cmd.E xecuteReader();
Once you're done with the data reader, call the Close method to close a
data reader:
reader.Close(); DataReader Properties(Shown in Table 10) Property Description Depth Indicates the depth of nesting for row FieldCount Returns number of columns in a row IsClosed Indicates whether a data reader is closed Item Gets the value of a column in native format RecordsAffected Number of row affected after a transaction Table 10 DataReader Properties
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ADO.Net The DataReader methods (Shown in Table 11) Method Description Close Closes a DataRaeder object. Read Reads next record in the data reader. NextResult Advances the data reader to the next result during batch
transactions. Getxxx There are dozens of Getxxx methods. These methods
read a specific data type value from a column. For
example. GetChar will return a column value as a
character and GetString as a string. Table 11 DataReader methods Reading with the DataReader ● The OleDbDataReader is initialized, utilizing its various methods to read data records. ● Read method, which, when called repeatedly, continues to read each row of data into the DataReader object. ● The DataReader also provides a simple indexer that enables to pull each column of data from the row. Example 5: create a connection object, create a command object, called the ExecuteReader method, called the DataReader's Read method until the end of the data, and then display the data. At the last, released the data reader and connection objects. using System;
using System.Collections.Generic;
using System.Text;
using System.Data.SqlClient;

namespace CommandTyp eEnumeration
{
class Program
{
static void Main(string[] args)
{
// Create a connection string
string ConnectionString = "Integrated Security = SSPI; " +
"Initial Catalog= Northwin d; " + " Data source = localhost; ";
string SQL = "SELECT * FROM Customers"; munotes.in

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// create a connection object
SqlConnection conn = new SqlConnection(ConnectionString);

// Create a command object
SqlCommand cmd = new SqlCommand(SQL, conn);
conn.Open();

// Call ExecuteReader to return a DataReader
SqlDataReader reader = cmd.ExecuteReader();
Console.WriteLine("customer ID, Contact Name, " + "Contact
Title, Address ");
Console.WriteLine("=============================");
while (reader.Read())
{
Console.Write(reader["CustomerID"].ToS tring() + ", ");
Console.Write(reader["ContactName"].ToString() + ", ");
Console.Write(reader["ContactTitle"].ToString() + ", ");
Console.WriteLine(reader["Address"].ToString() + ", ");
}

//Release resources
reader.Close();
conn.Close();
}
}
}

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ADO.Net 11.7 DISCONNECTED DATA ACCESS ● The ADO.NET Framework supports two models of Data Access Architecture, Connection Oriented Data Access Architecture and Disconnected Data Access Architecture. ● The ADO.NET Disconnected Data Access Architecture is far more flexible and powerful than ADOs Connection Oriented Data Access. ● In Connection Oriented Data Access Architecture the application makes a connection to the Data Source and then interacts with it through SQL requests using the same connection. ● The application stays connected to the database system even when it is not using any Database Operations. ● The DataSet is the central component in the ADO.NET Disconnected Data Access Architecture. ● A DataSet is an in-memory data store that can hold multiple tables at the same time. DataSet ds = new DataSet(); 11.8 SUMMARY 1. ADO.NET consists of managed classes that allow .NET applications to connect to data sources (relational databases), execute commands, and manage disconnected data. 2. ADO.NET uses a multilayered architecture that revolves around a few key concepts, such as Connection, Command, and DataSet objects. 3. The .NET Framework Data Provider for SQL Server (SqlClient) uses its own protocol to communicate with SQL Server. 4. A data reader provides an easy way for the programmer to read data from a database as if it were coming from a stream. 5. The ADO.NET Framework supports two models of Data Access Architecture, Connection Oriented Data Access Architecture and Disconnected Data Access Architecture. munotes.in

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166 .Net technology 11.9 REFERENCE FOR FURTHER READING 1. Beginning ASP.NET 4.5 in C#, Matthew MacDonald, Apress(2012) 2. The Complete Reference ASP .NET, MacDonald, Tata McGraw Hill 3. Beginning ASP.NET 4 in C# and VB Imar Spanajaars, WROX 11.10 UNIT END EXERCISES 1. What is ADO.NET? Explain the Data Provider Model? 2. Explain the ADO.NET Direct Data Access, with an example? 3. Write a short note on: a. Creating a Connection b. Select Command c. DataReader d. Disconnected Data Access  munotes.in

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167 12 DATA BINDING Unit Structure : 12.0 Objective 12.1 Introduction 12.2 Single-Value Data Binding, 12.3 Repeated-Value Data Binding, 12.4 Data Source Controls – SqlDataSource 12.5 Summary 12.6 Reference for further reading 12.7 Unit End Exercises 12.0 OBJECTIVE 1. To learn how data binding and the data source controls work. 2. To understand the single and repeated value data binding. 3. To study the SqlDataSource controls. 12.1 INTRODUCTION ● Data binding is an aspect that allows us to associate a data source with a control and have that control automatically display data. ● The main characteristic of data binding is that it’s declarative, not programmatic. That means data binding is defined outside program, alongside the controls in the .aspx page. ● The benefit is that it helps us achieve a cleaner separation between controls and program in a web page. ● In ASP.NET, most web controls (including TextBox, LinkButton, Image, and many more) support single-value data binding. With single-value binding, we can bind a control property to a data source, but the control can display only a single value. ● The property we bind doesn’t need to represent something directly visible on the page. ● For example, not only can we bind the text of a hyperlink by setting the Hyperlink.Text property, but we can also bind the NavigateUrl property to specify the target destination of the link. To use single-value binding, we create data binding expressions. munotes.in

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168 .Net technology ● Numerous web controls support repeated value binding, which means they can provide a set of items. ● Repeated value controls often create lists and grids (e.g. the ListBox and GridView are two examples). ● If a control supports repeated-value binding, it always uncovers a DataSource property, which accepts a data object. ● After setting the DataSource property, create the logical link from the server control to the data object that contains the data to render. ● The control’s DataBind() method, which loops through the data source, extracts its data, and provides it to the page. Repeated-value binding is by far the more poful type of data binding. 12.2 SINGLE-VALUE DATA BINDING ● The controls that support single-value data binding allow us to bind some of their properties to a data binding expression. ● This expression is entered in the .aspx markup portion of the page (not the program- behind file) and enclosed between the <%# and %> delimiters. Here’s an syntax: <%# expression_goes_here %> ● This looks like a script block, but it isn’t. While coding inside this tag, error will get The only thing we can add is valid data binding expressions. For example, if we have a public, protected, or internal variable in page class named EmployeeName, we could write the following: <%# EmployeeName %> ● To evaluate a data binding expression, you must call the Page.DataBind() method in program. ● While calling DataBind(), ASP.NET will examine all the expressions on page and replace them with the corresponding value. ● If we forget to call the DataBind() method, the data binding expression won’t be filled in instead, it just gets thrown away when page is rendered to HTML. ● The source for single-value data binding can include the value of a ○ property, ○ member variable, ○ return value of a function (as long as the property, member variable, or function has an accessibility of protected, public, or internal). munotes.in

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Data Binding ● It can also be any other expression that can be evaluated at runtime, such as a reference to another control’s property, a calculation using operators and literal values, and so on. ● The valid data binding expressions: <%# GetUserName() %> <%# 3 + (3 * 40) %> <%# "amit " + "raju" %> <%# Request.Browser.Browser %> ● Add data binding expressions just about anywhere on the page, then assign a data binding expression to a property in the control tag. ● Example 1 page that uses several data binding expressions:

NavigateUrl='<%# LogoPath.Value %>' Font-Bold="True" Text="Show
logo" />



<%# FilePath %>




Example 1 Data binding expressions ● We bind the Text property of a Label and a TextBox & use other properties such as the ImageUrl of an Image, the NavigateUrl property of a HyperLink, and the src attribute of a static HTML tag. ● After we put the binding expression elsewhere in the page without binding to any property or attribute. For example, the previous web page has a binding expression between the and tags. munotes.in

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170 .Net technology ● While it’s executing, the resulting text will be rendered on the page and rendered in bold type. Then place the expression outside the

section, as long as you don't try to insert a server-side control on a page. ● The expressions in this sample page refer to a FilePath property, a GetFilePath() function, and the Value property of a server-side hidden field that’s declared on the same page. To complete this page, need to define these ingredients in script blocks or in the program-behind class: (Shown in Example 2) protected string GetFilePath()
{
return "rose.gi f";
}
protected string FilePath
{
get { return "rose.gif"; }
} Example 2 FilePath property In this program, the property and function return only a hard-program string. However, we can also add just about any C# program to generate the value for the data binding expression dynamically. 12.3 REPEATED-VALUE DATA BINDING, ● Repeated-value binding allows to bind an entire list of information to a control. This list of information is represented by a data object that wraps a collection of items. This could be a collection of convention objects (e.g., an ordinary ArrayList or Hashtable) or a collection of rows (for e.g., with a DataReader or DataSet). ASP.NET includes several basic list controls that support repeated-value binding: ○ All controls that render themselves using the tag, including the HtmlSelect, ListBox, and DropDownList controls ○ The CheckBoxList and RadioButtonList controls, which render each child item with a separate checkbox or radio button. ○ The BulletedList control, which creates a list of bulleted or numbered points ● All controls display a single-value field of a property from each data item. When performing data binding with one of these controls, use the following listed properties. munotes.in

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Data Binding Data Properties for List Controls 1. DataSource This is a data object that contains a collection of data items to display. This data object must implement one of the interfaces that ASP.NET data binding supports, typically ICollection. 2. DataSourceID Instead of supplying the data object programmatically, link list control to a data source control by setting this property. The data source control will generate the required data object automatically. Use DataSource property or the DataSourceID property, but not both. 3. DataTextField Every data source represents a collection of data items. A list control displays only a single Value from each list item. The DataTextField denotes the field (row) or property (object) of the data item that contains the value to display in the page. 4. DataTextFormatString This property states an optional format string that the control will use to format each DataTextValue before displaying it. For example, state that a number should be formatted as a currency value. 5. DataValueField This property is related to the DataTextField property, but the value from the data item isn’t displayed in the page; rather, it’s stored in the value attribute of the underlying HTML tag. This enables retrieving the value afterwards in program. The primary use of this field is to store a unique ID or primary key field can use it later to retrieve more data when the user selects a specific item. Program for creating and binding the hashtable(shown in example 3): Example 3 protected void Page_Load(object sender, System.EventArgs e)
{
if (!Page.IsPostBack)
{
// Create the data source.
Hashtable ht = new Hashtable();
ht.Add("Key1", "red");
ht.Add("Key2", "blue");
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172 .Net technology // Set the DataSource property for the controls.
Select1.DataSource = ht;
Select2.DataSource = ht;
Listbox1.DataSource = ht;
Drop downList1.DataSource = ht;
CheckList1.DataSource = ht;
OptionList1.DataSource = ht;
// Bind the controls.
this.DataBind();
} Binding to a DataReader ● The above program used a hashtable as the data source. Are the Basic collections certainly not the only kind of data source, we can use with list data binding. alternatively, bind any data structure that implements the ICollection interface or one of its derivatives. The following list sum up many of these data classes: ○ All in-memory collection classes, ■ such as Collection, ■ ArrayList, ■ Hashtable, and ■ Dictionary ○ An ADO.NET DataReader object, which provides ■ connection-based, ■ forward-only, and ■ read-only access to the database. ○ The ADO.NET DataView, which provides a view onto a single disconnected DataTable object. ○ Any other custom object that implements the ICollection interface ● For example, I want to fill a list box with the full names of all the employees contained in the Employees table of the Northwind database. The Rich Data Controls ● In addition to the simple list controls, ASP.NET includes some rich data controls that support repeated value binding. The rich data controls are entirely a bit different from the simple list controls. munotes.in

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Data Binding ● They are designed only for data binding. They also have the capability to display various properties or fields from each data item, often in a table-based according to a template ● They support higher-level features such as editing and they provide several events that allow us to plug into the control’s inner workings at various points. The List of rich data controls: 1. GridView: The GridView is an all-purpose grid control for showing large tables of information. It supports selecting, editing, sorting, and paging. The GridView is the heavyweight of ASP.NET data controls. 2. DetailsView: The DetailsView is ideal for displaying a single record at a time, in a table that has one row per field. The DetailsView supports editing and optional paging controls that permit us to browse through an order of records. 3. FormView: Like the DetailsView, the FormView displays a single record at a time, supports editing, and provides paging controls for moving through a series of records. The difference is that the FormView is based on templates, which enable to combine fields in a much more flexible way that doesn’t need to be based on a table. Binding to a DataView ● There are few limitations when we bind directly to a DataReader. Because the DataReader is a forward-only cursor, we can’t bind data to multiple controls. we also won’t have the ability to apply custom sorting and filtering criteria on the fly. ● Finally, unless we take care to program page using generic interfaces such as IDataReader, we lock programs into the data provider we’re currently using, making it more difficult to modify or adapt programs in the future. To solve these problems, we can use the disconnected ADO.NET data objects. ● If we fill a disconnected DataSet, we can bind it to one or more controls, and we can tailor the sorting and filtering criteria. ● The DataSet is also completely generic no matter which data provider we use to fill DataSet, the DataSet itself looks the same. ● Never bind directly to a DataSet or DataTable object. Instead, we bind to a DataView object. ● A DataView represents a view of the data in a specific DataTable. That means the following example 4: munotes.in

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174 .Net technology Example 4: grid.DataSource = dataTable;
grid.DataBind();
is equivalent to this:
grid.DataSource = dataTable.DefaultView;
grid.DataBind(); ● Each DataTable includes a default DataView object that’s provided through the DataTable.DefaultView property. This skill allows it to bind directly to the DataTable. ● ASP.NET uses the default DataView automatically. The default DataView doesn’t apply any sort order and doesn’t filter out any rows. ● If we squeeze these settings, we can either configure the default DataView or create our own and explicitly bind it. then use all the sorting and filtering techniques. 12.4 DATA SOURCE CONTROLS – SQLDATASOURCE ● Data source controls, enables avoid writing any data access program. 1. SqlDataSource: This data source enables us to connect to any data source that has an ADO.NET data provider. This consists of SQL Server, Oracle, and the OLE DB or ODBC data sources. When using this data source, No need to write the data access program. 2. ObjectDataSource: This data source enables us to connect to a custom data access class. This is the preferred approach for large-scale professional web applications. 3. AccessDataSource: This data source enables us to read and write the data in an Access database file (.mdb). Access databases do not have a dedicated server engine like SQL Server that coordinates the actions of multiple people and ensures that data is unlikely lost or corrupted. For that reason, Access databases are best suited for very small websites, where few users need to manipulate data at the same time. A much better small-scale data solution is using the free SQL Server Express with the SqlDataSource control. 4. XmlDataSource: This data source allows us to connect to an XML file. 5. SiteMapDataSource: This data source allows us to connect to the Web.sitemap file that describes the navigational structure of the website. munotes.in

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Data Binding The Page Life Cycle with Data Binding ● Data source controls can perform two tasks: ○ They can retrieve data from a data source and supply it to linked controls. ○ They can update the data source when edits take place in linked controls. ● In order to know how data controls work, we need to know how they fit into the page life cycle. ● This awareness is important when we run into situations where we need to work with or extend the data binding model. For e.g., to add data or set a selected item in a control after it has been bound to the data source. ● Data binding tasks take place in this order: 1. The page object is created (based on the .aspx file). 2. The page life cycle begins, and the Page_init and Page.Load events fire. 3. All other control events fire. 4. The data source controls perform any updates. If a row is being updated, the Updating and Updated events fire. If a row is being inserted, the Inserting and Inserted events fire. If a row is being deleted, the Deleting and Deleted events fire. 5. The Page.PreRender event fires. 6. The data source controls perform any queries and insert the retrieved data in the linked controls. The Selecting and Selected events fire at this point. 7. The page is rendered and disposed of. The SqlDataSource ● Data source controls turn up in the .aspx markup portion of the web page like ordinary controls. ● Example: ● The SqlDataSource acts as a database connection that uses an ADO.NET provider. ● The SqlDataSource needs a generic way to create the Connection, Command, and DataReader objects it requires. ● The only way this is possible is if the data provider comprises a data provider factory. munotes.in

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176 .Net technology ● The factory has the responsibility of creating the provider specific objects that the SqlDataSource requires in order to access the data source. ● .NET craft with these four provider factories: ○ System.Data.SqlClient ○ System.Data.OracleClient ○ System.Data.OleDb ○ System.Data.Odbc ● These are registered in the machine.config file, and as a result we can use any of them with the SqlDataSource. we select a data source by setting the provider name. Here is a SqlDataSource that connects to a SQL Server database: ● The next step, to supply the required connection string without it, we cannot make any connections. ● All times place it in the section of the web.config file to guarantee greater flexibility and ensure not inadvertently changing the connection string, which minimizes the effectiveness of connection pooling. ● Example 5, if we create this connection string: Example 5

connectionString="DataSource=localhost;Initial
Catalog=Northwind;
Integrated Security=SSPI"/>

...
● SqlDataSource using a $ expression like this: ● After specifying the provider name and connection string, the next step is to add the query logic that the SqlDataSource will use when it connects to the database. ● Use each SqlDataSource control, created to retrieve a single query. munotes.in

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Data Binding ● Optionally, we can add corresponding commands for deleting, inserting, and updating rows. ● Example, one SqlDataSource is enough to query and update the Customers table in the Northwind database. Need two SqlDataSource controls, if we need to independently retrieve or update Customers and Orders information. ● The SqlDataSource command logic is supplied through four properties: ○ SelectCommand ○ InsertCommand ○ UpdateCommand ○ DeleteCommand, ○ Each command takes a string. The string we supply can be inline SQL ■ SelectCommandType, ■ InsertCommandType, ■ UpdateCommandType, ■ DeleteCommandType ● SqlDataSource that defines a SELECT command for retrieving records. (shown in example 6) Example 6: Employee s table:
ProviderName="System.Data.SqlClient" ConnectionString="<%$
ConnectionStrings:Northwind %>" SelectCommand="SELECT
EmployeeID, FirstName, LastName, Title, City FROM Employees"/> ● Working of Data Source Controls 1. Select the data source control, and click Refresh Schema in the smart tag. This step triggers the data source control to connect to the database and retrieve the column information for query. 2. Add a ListBox to form. Set the ListBox.DataSourceID property to the data source control. we can choose it from a drop-down list that shows all the data sources on the form. 3. Set the ListBox.DataTextField to the column we want to display (in this case, choose EmployeeID). The list of fields should also be provided in a drop-down list. munotes.in

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178 .Net technology 4. Use the same steps to bind a rich data control. Add a GridView to the web page, and set the GridView.DataSourceID property to the same data source. 5. Run a web page. Don’t fret about executing the command or calling DataBind() on the page ASP.NET performs both of those tasks automatically. Disadvantages of the SqlDataSource 1. Data access logic embedded in the page: To create a SqlDataSource control, we need to hard-program the SQL statements in the web page. 2. Maintenance in large applications: Every page that accesses the database needs its own set of SqlDataSource controls. This can turn into a maintenance nightmare, particularly if we have several pages using the same query. 3. Lack of flexibility: Every data access task requires a separate SqlDataSource. If we want to provide a user with multiple ways to view or query data, this can swamp web pages with data source objects, one for each command variant. This can get complicated fast. 4. Inapplicability to other data tasks: The SqlDataSource does not properly represent some types of tasks. The SqlDataSource is planned for data display and data editing scenarios. However, this model divides up if we need to connect to the database and perform another task, such as placing a shipment request into an order pipeline or logging an event. 12.5 SUMMARY ● We have studied data binding expressions and the ASP.NET data source controls in detail. ● The use of GridView, ASP.NET’s premier rich data control. ● The main characteristic of data binding is that it’s declarative, not programmatic. That means data binding is defined outside the program, alongside the controls in the .aspx page. ● The controls that support single-value data binding allow us to bind some of their properties to a data binding expression. ● Repeated-value binding allows to bind an entire list of information to a control. ● Data source controls, enables avoid writing any data access program. ● Data source controls turn up in the .aspx markup portion of the web page like ordinary controls. munotes.in

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Data Binding 12.6 REFERENCE FOR FURTHER READING 1. Beginning ASP.NET 4.5 in C#, Matthew MacDonald, Apress(2012) 2. The Complete Reference ASP .NET, MacDonald, Tata McGraw Hill 3. Beginning ASP.NET 4 in C# and VB Imar Spanajaars, WROX 12.7 UNIT END EXERCISES 1. What is data binding? Explain Single-Value Data Binding & Repeated-Value Data Binding? 2. List the Disadvantages of the SqlDataSource 3. Explain the Page Life Cycle with Data Binding.  munotes.in

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180 .Net technology 13 DATA CONTROLS Unit Structure : 13.0 Objective 13.1 Introduction 13.2 GridView 13.3 DetailsView 13.4 FormView 13.5 Summary 13.6 Reference for further reading 13.7 Unit End Exercises 13.0 OBJECTIVE ● To understand ASP.NET's rich data controls, such as the GridView. ● We will take a closer look at the three most powerful data controls. ● To learn how to fine-tune formatting and use features such as selection, sorting, filtering, and templates. ● To learn about advanced scenarios such as showing images, calculating summaries, and creating a master-details list in a single control. 13.1 INTRODUCTION ● In .NET technologie the MultiView is that unlike the rich data controls (the GridView, FormsView, and so on), ● The MultiView is not a naming container. This means that if We add a control named textBox1 to a view, we can’t add another control named textBox1 to another view. ● There’s no real difference between the controls. We add a view and controls in the rest of the page. ● The controls created will be accessible through member variables in page class. This means it’s easy to configure a control in the second view when an event is raised by a control in the first view. ● As a result, the pages created using the MultiView tend to be heavier than normal pages. because the entire control model including the controls from every view is created on every postback and persisted to view state. F munotes.in

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Data Controls ● Example, if We have three views and each view has a different data source control, each time the page is posted back all three data source controls will perform their queries, and every view will be bound, including those that aren’t currently visible. To avoid this overhead, We can leave controls unbound and binding them programmatically, else canceling the binding process for views that aren’t currently visible. 13.2 GRIDVIEW ● The GridView is an extremely flexible grid control for showing data in a basic grid consisting of rows and columns. ● It includes a wide range of hard-wired features, including selection, paging, sorting, and editing, and it is extensible through templates. ● The great benefit of the GridView over the DataGrid is its support for code-free scenarios. ● Using the GridView, We can achieve many common tasks, such as paging and selection, without writing any code. ● With the DataGrid, We were forced to handle events to implement the same quality. Defining Columns ● When the property is set, the GridView uses reflection to examine the data object and finds all the fields (of a record) or properties (of a custom object). It then creates a column for each one, in the order that it finds it. ● This automatic column generation is fine for creating quick test pages, but it does not give the flexibility. For example, to hide columns, change their order, or configure some aspect of their display, such as the formatting or heading text. Set AutoGenerateColumns to false and define the columns in the section of the GridView control tag. Different types of column, as shown below The order of column tags find the right-to-left order of columns in the GridView. Shown in Table 1 Column Description BoundField
This column displays text from a field in the data
source. ButtonField
This column displays a button for each item in the list. CheckBoxField This column displays a check box for each item in the
list. It’s used
automatically for true/false fields (in SQL Server, these
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182 .Net technology Column Description CommandField This column provides selection or editing buttons. HyperLinkField This column displays its contents (a field from the data
source or static text) as a hyperlink. ImageField This column displays image data from a binary field
(providing it
can be successfully interpreted as a supported image
format). TemplateField This column allows We to specify multiple fields,
custom controls,
And arbitrary HTML using a custom template. It gives
us the highest degree of control but requires the most
work. Table 1 GridView Column ● BoundField is the most basic column type, which binds to one field in the data object. For example, here’s the definition for a single data-bound column that displays the EmployeeID field: ● When first creating a GridView, the AutoGenerateColumns property is not set (and so the default value of true is used). When We bind it to a data source control, nothing changes. ● If We click the Refresh Schema link of the data source control, the AutoGenerateColumns property is flipped to false, and Visual Studio adds a tag for each field it finds in the data source. This approach has several advantages: ○ Easy to use fine-tune column order, column headings, and other details by tweaking the properties of column objects. ○ Can hide columns We don’t want to show by removing the column tag. ○ Explicitly defined columns are faster than autogenerated columns. That’s because auto generated columns force the GridView to reflect on the data source at runtime. ○ Can add extra columns to the mix for selecting, editing, and more. Example 1 shows the complete GridView declaration with explicit columns: Example 1: DataSourceID="sourceEmployees"
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Data Controls







ConnectionString="<%$ ConnectionStrings:Northwind %>"
ProviderName="System.Data.SqlClient" SelectC ommand=
"SELECT EmployeeID, FirstName, LastName, BirthDate, Title, City
FROM Employees">
● Properties: DataField This property indicates the name of the field (for a row) or property (for an object) of the data item that We want to display in this column. DataFormatString This property formats the field. This is useful for getting the right representation of numbers and dates. ApplyFormatInEditMode If true, the format string will be used to format the value even when it appears in a text box in edit mode. The default is false, which means only the underlying normal will be used. HeaderText, FooterText,and HeaderImageUrl The first two properties set the text in the header and footer region of the grid, if this grid has a header (GridView.ShowHeader is true) and footer (GridView.ShowFooter is true). The header is most commonly used for a descriptive label such as the field name, while the footer can contain a dynamically calculated value such as a summary. To show an image in the header instead of text, set the HeaderImageUrl property. munotes.in

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184 .Net technology ReadOnly If true, the value for this column can’t be changed in edit mode. No edit control will be provided. Primary key fields are often read-only. InsertVisible If false, the value for this column can’t be set in insert mode. If We want a column value to be set programmatically or based on a default value defined in the database, We can use this feature. Visible If false, the column won’t be visible in the page (and no HTML will be rendered for it). This property gives We a convenient way to programmatically hide or show specific columns, changing the overall view of the data. SortExpression This property specifies an expression that can be appended to a query to perform a sort based on this column. It’s used in conjunction with sorting, as described in the “Sorting the GridView” section. HtmlEncode If true (the default), all text will be HTML encoded to prevent special characters from mangling the page. You could disable HTML encoding if We want to embed a working HTML tag (such as a hyperlink), but this approach isn’t safe. It’s always a better idea to use HTML encoding on all values and provide other functionality by reacting to GridView selection events. NullDisplayText This property defines the text that will be displayed for a null value. The default is an empty string, although We could change this to a hard- coded value, such as “(not specified).” ConvertEmptyStringToNull If this is true, before an edit is committed, all empty strings will be converted to null values. ControlStyle, HeaderStyle, FooterStyle, and ItemStyle These properties configure the appearance for just this column, overriding the styles for the row. ● If We don’t want to configure columns by hand, select the GridView, and click the ellipsis (...) next to the Columns property in the Properties window. You’ll see a Fields dialog box that lets We add, remove, and refine With columns, shown in figure 1 munotes.in

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Data Controls
Figure 1. Configuring columns in Visual Studio In the following sections, implement these topics: 1. Formatting: How to format rows and data values 2. Selecting: How to let users select a row in the GridView and respond accordingly 3. Sorting: How to dynamically reorder the GridView in response to clicks on a column header 4. Paging: How to divide a large result set into multiple pages of data, using both automatic and custom paging code 5. Templates: How to take complete control of laWet, formatting, and editing by defining templates 13.3 DETAILSVIEW ● The GridView and ListView excel at showing dense tables with multiple rows of information. However, sometimes We want to provide a detailed look at a single record. ● ASP.NET includes two controls that are tailored for this purpose: the DetailsView and FormView. ● Both show a single record at a time but can include optional pager buttons that let We step through a series of records. Both support templates, but the FormView requires them. This is the key distinction between the two controls. ● The FormView gives the most flexibility. But if We want to avoid the complexity of templates, the DetailsView gives a simpler model that lets We build a multi row data display out of field objects, in much the same way that the GridView is built out of column objects.
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186 .Net technology ● We can get up to speed with the DetailsView and FormView quite quickly. That’s because both the DetailsView and the FormView borrow a portion of the GridView model. The DetailsView ● The DetailsView is designed to display a single record at a time. It places each piece of information in a separate row of a table. ● The DetailsView can also bind to a collection of items. In this point, it shows the first item in the group. ● It also allows to move from one record to the next using paging controls, ● We can configure the paging controls using the PagingStyle and PagingSettings properties ● The only difference is that there’s no support for custom paging, which means the full data source object is always retrieved. ● It’s tempting to use the DetailsView pager controls to make a handy record browser. Unfortunately, this approach can be quite inefficient. ● First, a separate postback is required each time the user moves from one record to another. But the real drawback is that each time the page is posted back, the full set of records is retrieved, even though only a single record is shown. ● If We opted to implement a record browser page with the DetailsView, at a bare minimum it must enable caching to reduce the database work . Example 2: Create a drop-down list and bind this to a data source that queries just the employee names. Then, when a name is selected from the list, retrieve the full details for just that record using another data source. (shown in figure 2)
Figure 2. The DetailsView with paging
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Data Controls Defining Fields ● The DetailsView uses reflection to generate the fields it shows. ● It observes the data object and creates a separate field for each field (in a row) or property (in a custom object), just like the GridView. ● To disable this automatic field generation by setting AutoGenerateRows to false. It’s then up to us to declare the field objects. Example 3: Fields from the data item are represented with the BoundField tag, buttons can be created with the ButtonField, and so on. Example 3 Field declarations for a DetailsView: DataSourceID="sourceEmployees"
AutoGenerateRows="False">

/>



HeaderText="TitleOfCourtesy" />

...

...
Record Operations ● The DetailsView holds delete, insert, and edit operations. ● GridView, We don't need to add a CommandField with edit controls. In lieu, We simply set the ○ Boolean AutoGenerateDeleteButton, ○ AutoGenerateEditButton, and ○ AutoGenerateInsertButton properties on the DetailsView control. ● This adds a CommandField at the bottom of the DetailsView with links for these tasks. munotes.in

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188 .Net technology ● After clicking on the Delete button, the delete operation is performed immediately. However, when We click an Edit or Insert button, the DetailsView changes into edit or insert mode. ● The DetailsView has three modes (as represented by the DetailsViewMode enumeration). ● These modes are ReadOnly, Edit, and Insert. ● Find the current mode at any time by checking the CurrentMode property, and can call ChangeMode() to change it. ● Use the DefaultMode property to create a DetailsView that always begins in edit or insert mode. ● In edit mode, the DetailsView uses standard text box controls just like the GridView. (shown in figure 3)
Figure 3. Editing in the DetailsView 13.4 FORMVIEW ● The FormView provides a template-only control for displaying and editing a single record. ● The vision of the FormView template model is that it matches the model of the TemplateField in the GridView quite closely. ● Following are the templates to work with: ○ ItemTemplate ○ EditItemTemplate ○ InsertItemTemplate ○ FooterTemplate ○ HeaderTemplate ○ EmptyDataTemplate ○ PagerTemplate ● This way can take the exact template content which is put in a TemplateField in a GridView (shown in example 4) and place it inside the FormView.
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Data Controls Example 4: DataSourceID="sourceEmployees">


<%# Eval("EmployeeID") %> -
<%# Eval("TitleOfCourtesy") %> <%# Eval("FirstName") %>
<%# Eval("LastName") %>

---

<%# Eval("Address") %>

<%# Eval("City") %>, <%# Eval("Country") %>,
<%# Eval("PostalCode") %>

<%# Eval("HomePhone") %>



<%# Eval("Notes") %>





● The DetailsView, the FormView works in three distinct modes: read-only, insert, and edit. ● The FormView control doesn’t support the CommandField class that automatically creates editing buttons. Table 2 shows the lists of recognized command names: Command
Name Description Where It Be longs Edit Puts the FormView into edit
mode. The FormView renders
the current record using the
EditItemTemplate with the edit
controls We’ve defined. The ItemTemplate Cancel Cancels the edit or insert
operation and returns to the
mode specified by the
DefaultMode property. Usually,
this will be normal mode
(FormViewMode.ReadOnly),
and the FormView will display
the current record using the
ItemTemplate. The EditItemTemplate
and
InsertItemTemplate Update Applies the edit and raises the
ItemUpdating and ItemUpdated
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190 .Net technology Command
Name Description Where It Be longs New Puts the FormView in insertion
mode. The FormView displays
a new, blank record using the
InsertItemTemplate with the
edit controls We’ve defined. The ItemTemplate Insert Inserts the newly supplied data
and raises the ItemInserting and
ItemInserted events on the way. The
InsertItemTemplate Delete Removes the current record
from the data source, raising the
ItemDeleting and ItemDeleted
events. Does not change the
FormView mode. The ItemTemplate Table 2 List of Command 13.5 SUMMARY 1. We have learned how to build rich data-bound pages. 2. The GridView and considered its support for formatting, selection, sorting, paging, templates, and editing. 3. We considered the template-based ListView and the data controls that are designed to work with a single record at a time: the DetailsView and FormView. 4. We are looking at several common advanced scenarios with data-bound pages. 13.6 REFERENCE FOR FURTHER READING 1. Beginning ASP.NET 4.5 in C#, Matthew MacDonald, Apress(2012) 2. The Complete Reference ASP .NET, MacDonald, Tata McGraw Hill 3. Beginning ASP.NET 4 in C# and VB Imar Spanajaars, WROX 13.7 UNIT END EXERCISES 1. What is GridView? Explain the List of Column use. 2. What are the different properties used in GridView? 3. What is FormView? Explain the list of recognized commands names?  munotes.in

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191 14 WORKING WITH XML Unit Structure : 14.0 Objective 14.1 Introduction 14.2 Working with XML 14.3 XML Classes 14.4 XMLTextWriter, 14.5 XMLTextReader 14.6 Summary 14.7 Reference for further reading 14.8 Unit End Exercises 14.0 OBJECTIVE ● To understand the use of XML over the internet ● To study the XML classes. ● To study XMLTextWriter & XMLTextReader classes. 14.1 INTRODUCTION ● XML stands for EXtensible Markup Language XML is a markup language much like HTML. XML was designed to describe data ● XML tags are not predefined. You must define your own tags ● XML shall support a wide variety of applications ● XML is already being used for exchanging information among financial programs, for distributing and updating programs, for writing invoices for delivery over the phones ● XML shall be compatible with SGML ● It shall be easy to write programs which process XML documents. ● XML documents should be human readable and reasonably clear ● The XML should be prepared quickly. ● XML should be easy to create. ● XML uses a Document Type Definition (DTD) or an XML Schema to describe the data munotes.in

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192 .Net technology ● XML with a DTD or XML Schema is designed to be self-descriptive ● But unlike HTML, XML tags identify the data rather than specify how to display it. Whereas an HTML tag says something like, "Display this data in bold font" (...), an XML tag acts like a field name in your program. It puts a label on a piece of data that identifies it (for example, ...) shown in example 1. Example 1 of messaging application:
you@yourAddress.com
me@myAddress.com
XML Is Really Cool

How many ways is XML cool? Let me count the ways...

Advantages of XML ● When XML was first introduced, its success was partly due to its simplicity. ● The rules of XML are much shorter and simpler than the rules of its predecessor, SGML (full form Standard Generalized Markup Language), and simple XML documents are human-readable. ● However, using XML in a professional application isn’t simple at all. But if anything, XML is much more useful today than it ever was before. ● The benefits of using XML in a modern application include the following: ○ Adoption: XML is ubiquitous. Many companies are using XML to store data or are actively considering it. Whenever data needs to be shared, XML is automatically the first choice that’s Inspect. ○ Extensibility and flexibility: XML imposes no rules about data semantics and does not tie companies into proprietary networks, unlike EDI (Electronic Data Interchange). XML can fit any type of data and is cheaper to implement. ○ Related standards and tools: Another reason for XML’s success is the tools (such as parsers) and the surrounding munotes.in

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Working with XML standards (such as XML Schema, XPath, and XSLT) that help in creating and processing XML documents. As a result, programmers in nearly any language have ready-made components for reading XML, verifying that XML is valid, verifying XML against a set of rules (known as a schema), searching XML, and transforming one format of XML into another. ● XML acts like the glue that allows different systems to work together. ● It helps standardize business processes and transactions between organizations. 14.2 WORKING WITH XML ● XML was designed to store, carry and exchange data. It was not designed to display data. ● An XML application is normally defined by creating a document type definition DTD which is an optional component of an XML document. ● A DTD is like a database schema. It defines and names the elements that can be used in the document, the order in which the elements will appear, the element attributes that can be used etc. ● To use an XML application you usually include its DTD in your XML document. Having the DTD in the document restricts the elements and structure that you can use so that your document is forced to conform to the application standard. ● Uses of XML in real world ❖ Storing Databases. ❖ Structuring documents. ❖ Storing Vector Graphics (VML). ❖ Describing Multimedia Applications ❖ Defining channels. ❖ Describing software packages and the interdependencies. ❖ Communicating among applications. ❖ Sending electronic business cards vie e-mai. ❖ XML can Separate Data from HTML. ❖ With XML, your data is stored outside your HTML. ● When HTML is used to display data, the data is stored inside your HTML. With XML, data can be stored in separate XML files. This munotes.in

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194 .Net technology way you can concentrate on using HTML for data layout and display, and be sure that changes in the underlying data will not require any changes to your HTML. ● XML data can also be stored inside HTML pages. ● XML is used to Exchange Data ● XML, data can be exchanged between incompatible systems. XML and B2B ● With the XML, financial information can be exchanged over the Internet. ● XML is going to be the main language for exchanging financial information between businesses over the Internet. ● XML can be used to Share Data ● With XML, plain text files can be used to share data. ● Since XML data is stored in plain text format, XML provides a software- and hardware-independent way of sharing data. This makes it much easier to create data that different applications can work with. ● It also makes it easier to expand or upgrade a system to new operating systems, servers, applications, and new browsers. ● XML can be used to Store Data ● With XML, plain text files can be used to store data. ● XML can also be used to store data in files or in databases. Applications can be written to store and retrieve information from the store, and generic applications can be used to display the data. ● XML can make your Data more Useful ● With XML, your data is available to more users. ● XML can be used to Create new Languages ● XML is the mother of WAP and WML. The Wireless Markup Language (WML), used to markup Internet application for handheld devices like mobile phones, is written in XML ● Displaying XML Documents ● Style Sheet Linking ○ You can use a Cascading Style Sheet which is used for HTML or an XSL-eXtensible Style Language which is specifically used for the XML. XSL is more powerful than CSS. munotes.in

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Working with XML ● Data binding ○ This requires you to create an HTML page and link the XML document to it and bind standard HTML elements such as tables to the XML elements. ● Scripting ○ You create an HTML page, link the XML document to it and access and display individual XML by writing script code (Javascript or Vbscript. The browser then exposes the XML document as a Document Object Model- DOM. 14.3 XML CLASSES ● The .NET framework contains a rich set of classes for working with XML data. ● Classes are divided into multiple namespaces. ● The main classes for working with XML data are as follows : ○ XmlTextReader ■ This class provides fast, forward-only access to the raw data contained in an XML file. It parses XML data into tokens, but it does not represent the XML data in an object model such as the W3C XML Document Object Model (DOM). ○ XmlTextWriter ■ This class provides a fast, forward-only method to write data to an XML file. It ensures that the data written to the file conforms to the W3C XML 1.0 standard. ○ XmlDocument ■ This class represents XML using the W3C XML DOM levels 1 and 2. You can use this class to both navigate and edit the nodes in an XML document tree. ○ XmlDataDocument ■ This class enables you to represent both XML and relational data in W3C XML DOM levels 1 and 2. You can use this class with a DataSet to provide both relational and non-relational views of the same underlying data. ○ XmlNodeReader ■ This class provides fast, forward-only access to data represented by the XmlDocument or XmlDataDocument class. ○ DocumentNavigator munotes.in

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196 .Net technology ■ This class enables you to efficiently navigate an XML document represented by the XmlDocument class. It supports the XPath data model for navigation. ○ DataDocumentNavigator ■ This class enables you to efficiently navigate an XML document represented by the XmlDataDocument class. It supports the XPath data model for navigation. ○ XslTransform ■ This class enables you to transform an XML document with XSL stylesheets. It supports XSLT 1.0 stylesheet syntax. 14.4 XMLTEXTWRITER ● This class represents a writer that provides a fast, non-cached, forward-only way of generating streams or files containing XML data that conforms to the W3C Extensible Markup Language (XML) 1.0 and the Namespaces in XML recommendations. public class XmlTextWriter : System.Xml.XmlWriter ● XmlTextWriter maintains a namespace stack corresponding to all the namespaces defined in the current element stack. Using XmlTextWriter you can declare namespaces manually which is shown below example 2. Example 2 w.WriteStartElement("root");
w.WriteAttributeString("xmlns", "x", null, "urn:1");
w.WriteStartElement("item","urn:1");
w.WriteEndElement();
w.WriteStartElement("item","urn:1");
w.WriteEndElement();
w.WriteEndElement(); ● XmlTextWriter promotes the namespace declaration to the root element to avoid having it duplicated on the two child elements. The child elements pick up the prefix from the namespace declaration. Shown in example 3. Example 3: root elements


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Working with XML ● XmlTextWriter also allows you to override the current namespace declaration. In the following example, the namespace URI "123" is overridden by "abc" to produce the XML element Shown in example 4. Example 4: w.WriteStartElement("x","node","123");
w.WriteAttributeString("xmlns","x",null,"abc"); ● By using the write methods that take a prefix as an argument you can also specify which prefix to use. In the following example, two different prefixes are mapped to the same namespace URI to produce the XML text . Shown in example 5 Example 5: XmlTextWriter w = new XmlTextWriter(Console.Out);
w.WriteStartElement("x","root","urn:1");
w.WriteStartElement("y","item","urn:1");
w.WriteEndElement();
w.WriteEndElement();
w.Close(); ● If namespace conflicts occur, XmlTextWriter resolves them by generating alternate prefixes.(Shown in Table 1) For example, if an attribute and element have the same prefix but different namespaces, XmlWriter generates an alternate prefix for the attribute. The generated prefixes are named n{i} where i is a number beginning at 1. The number is reset to 1 for each element. Constructors XmlTextWriter(TextWriter) Creates an instance of the XmlTextWriter
class using the specified TextWriter. XmlTextWriter(Stream,
Encoding) Creates an instance of the XmlTextWriter
class using the specified stream and
encoding. XmlTextWriter(String,
Encoding) Creates an instance of the XmlTextWriter
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198 .Net technology ● Properties of XmlTextWriter shown in table 2 Properties BaseStream Gets the underlying stream object. Formatting Indicates how the output is formatted. Indentation Gets or sets how many IndentChars to write for each level
in the hierarchy when Formatting is set to
Formatting.Indented. IndentChar Gets or sets which character to use for indenting when
Form atting is set to Formatting.Indented. Namespaces Gets or sets a value indicating whether to do namespace
support. QuoteChar Gets or sets which character to use to quote attribute
values. Settings Gets the XmlWriterSettings object used to create this
XmlWriter instance. WriteState Gets the state of the writer. XmlLang Gets the current xml:lang scope. XmlSpace Gets an XmlSpace representing the current xml:space
scope. Table 2 XmlTextWriter Properties ● Methods of XmlTextWriter shown in table 3 Methods Close() Closes this stream and the underlying stream. Dispose() Releases all resources used by the current
instance of the XmlWriter class. Dispose(Boolean) Releases the unmanaged resources used by the
XmlWriter and optionally releases the managed
resources. DisposeAsync() Performs application -defined tasks associated
with freeing, releasing, or resetting unmanaged
resources asynchronously. DisposeAsyncCore( ) Performs application -defined tasks associated
with freeing, releasing, or resetting managed
resources asynchronously. Equals(Object) Determines whether the specified object is equal
to the current object. Flush() Flushes whatever is in the buffer to the
underlying streams and also flushes the
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Working with XML FlushAsync() Asynchronously flushes whatever is in the buffer
to the underlying streams and also flushes the
underlying stream. GetHashCode() Serves as the default hash function. GetType() Gets the Type of the current instance. LookupPrefix(String) Returns the closest prefix defined in the current
namespace scope for the namespace URI. MemberwiseClone() Creates a shallow copy of the current Object. ToString() Returns a string th at represents the current
object. WriteAttributes(XmlR
eader, Boolean) When overridden in a derived class, it writes out
all the attributes found at the current position in
the XmlReader. WriteAttributesAsync(
XmlReader, Boolean) Asynchronously writes out all the attributes
found at the current position in the XmlReader. WriteAttributeString(S
tring, String) When overridden in a derived class, it writes out
the attribute with the specified local name and
value. Table 3 Methods of XmlWriter class 14.5 XMLTEXTREADER ● This class represents a reader that provides fast, non-cached, forward-only access to XML data. public class XmlTextReader : System.Xml.XmlReader, System.Xml.IXmlLineInfo, System.Xml.IXmlNamespaceResolver ● XmlTextReader provides forward-only, read-only access to a stream of XML data. The current node refers to the node on which the reader is positioned. The reader is advanced using any of the read methods and properties reflect the value of the current node. ● This class implements XmlReader and conforms to the W3C Extensible Markup Language (XML) 1.0 and the Namespaces in XML recommendations. ● XmlTextReader provides the following functionality: ○ Enforces the rules of well-formed XML. ○ XmlTextReader does not provide data validation. ○ Check that DocumentType nodes are well-formed. XmlTextReader checks the DTD for well-formedness, but does not validate using the DTD. munotes.in

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200 .Net technology ○ For nodes where NodeType is XmlNodeType.EntityReference, a single empty EntityReference node is returned (that is, the Value property is String.Empty). ● Does not expand default attributes. ● XmlTextReader does not perform the extra checks required for data validation, ● XmlTextReader provides a fast well-formed parser. ● XmlTextReader throws an XmlException on XML parse errors. After an exception is thrown the state of the reader is not predictable. For example, the reported node type may be different from the actual node type of the current node. Use the ReadState property to check whether a reader is in error state. XmlTextReader Constrctor show in table 4 Constructors XmlTextReader() Initializes a new instance of the
XmlTextReader. XmlTextReader(Stream) Initializes a new instance of the
XmlTextReader class with the
specified stream. XmlTextReader(Stream,
XmlNameTable) Initializes a new instance of the
XmlTextReader class with the
specified stream and XmlNameTable. XmlTextReader(Stream,
XmlNodeType,
XmlParserContext) Initializes a new instance of the
XmlTextReader class with the
specified stream, XmlNodeType, and
XmlParserContext. XmlTextReader(String) Initializes a new instance of the
XmlTextReader class with the
specified file. XmlTextReader(String, Stream) Initializes a new instance of the
XmlTex tReader class with the
specified URL and stream. XmlTextReader(String, Stream,
XmlNameTable) Initializes a new instance of the
XmlTextReader class with the
specified URL, stream and
XmlNameTable. XmlTextReader(String,
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Working with XML specified URL and TextReader. XmlTextReader(String,
TextReader, XmlNameTable) Initializes a new instance of the
XmlTextReader class with the
specified URL, TextReader and
XmlNameTable. XmlTex tReader(String,
XmlNameTable) Initializes a new instance of the
XmlTextReader class with the
specified file and XmlNameTable. XmlTextReader(String,
XmlNodeType,
XmlParserContext) Initializes a new instance of the
XmlTextReader class with the
specified str ing, XmlNodeType, and
XmlParserContext. XmlTextReader(TextReader) Initializes a new instance of the
XmlTextReader class with the
specified TextReader. XmlTextReader(TextReader,
XmlNameTable) Initializes a new instance of the
XmlTextReader class with the
specified TextReader and
XmlNameTable. XmlTextReader(XmlNameTable) Initializes a new instance of the
XmlTextReader class with the
specified XmlNameTable. Table 4 Constructor for XmlTextReader Properties (shown in below table 5) AttributeCount Gets the number of attributes on the current
node. BaseURI Gets the base URI of the current node. CanReadBinaryContent Gets a value indicating whether the
XmlTextReader implements the binary content
read methods. CanReadValueChunk Gets a value indicating whether the
XmlTextReader implements the
ReadValueChunk(Char[], Int32, Int32)
method. CanResolveEntity Gets a value indicating whether this reader can
parse and resolv e entities. Depth Gets the depth of the current node in the XML
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202 .Net technology Encoding Gets the encoding of the document. EntityHandling Gets or sets a value that specifies how the
reader handles entities. EOF Gets a value indicating whether the reader is
positioned at the end of the stream. HasAttributes Gets a value indicating whether the current
node has any attributes.
(Inherited from XmlReader) HasValue Gets a value indicating whether the current
node can have a Value other than
String.Empty. IsDefault Gets a value indicating whether the current
node is an attribute that was generated from the
default value defined in the DTD or schema. IsEmptyElement Gets a value indicating whether the current
node is an empty element (for example,
). Item[Int32] When overridden in a derived class, gets the
value of the attribute with the specified index.
(Inherited from XmlReader) Item[String, String] Whe n overridden in a derived class, gets the
value of the attribute with the specified
LocalName and NamespaceURI.
(Inherited from XmlReader) Item[String] When overridden in a derived class, gets the
value of the attribute with the specified Name.
(Inherited from XmlReader) LineNumber Gets the current line number. LinePosition Gets the current line position. LocalName Gets the local name of the current node. Name Gets the qualified name of the current node. Namespaces Gets or sets a value indic ating whether to do
namespace support. NamespaceURI Gets the namespace URI (as defined in the
W3C Namespace specification) of the node on
which the reader is positioned. NameTable Gets the XmlNameTable associated with this
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Working with XML Normalization Gets or sets a value indicating whether to
normalize white space and attribute values. Prefix Gets the namespace prefix associated with the
current node. ProhibitDtd Obsolete.
Gets or sets a value indicating whether to allow
DTD processing. This property is obsolete.
Use DtdProcessing instead. QuoteChar Gets the quotation mark character used to
enclose the value of an attribute node. ReadState Gets the state of the reader. SchemaInfo Gets the schema information that has been
assigned to the current node as a result of
schema validation.
(Inherited from XmlReader) Settings Gets the XmlReaderSettings object used to
create this XmlReader instance.
(Inheri ted from XmlReader) Value Gets the text value of the current node. ValueType Gets The Common Language Runtime (CLR)
type for the current node.
(Inherited from XmlReader) WhitespaceHandling Gets or sets a value that specifies how white
space is handled. XmlLang Gets the current xml:lang scope. XmlResolver Sets the XmlResolver used for resolving DTD
references. XmlSpace Gets the current xml:space scope. Table 5 Properties for XmlTextReader Methods (Shown in table 6) Close() Changes the ReadState to Closed. Dispose() Releases all resources used by the
current instance of the XmlReader class.
(Inherited from XmlReader) Dispose(Boolean) Releases the unmanaged resources used
by the XmlReader and optionally
releases the managed resources.
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204 .Net technology Equals(Object) Determines whether the specified object
is equal to the current object.
(Inherited from Object) GetAttribute(Int32) Gets the value of the attribute with the
specifi ed index. GetAttribute(String) Gets the value of the attribute with the
specified name. GetAttribute(String, String) Gets the value of the attribute with the
specified local name and namespace
URI. GetHashCode() Serves as the default hash function.
(Inherited from Object) GetNamespacesInScope
(XmlNamespaceScope) Gets a collection that contains all
namespaces currently in -scope. GetRemainder() Gets the remainder of the buffered XML. GetType() Gets the Type of the current instance.
(Inherited from Object) GetValueAsync() Asynchronously gets the value of the
current node.
(Inherited from XmlReader) HasLineInfo() Gets a value indicating whether the class
can return line information. IsStartElement() Calls MoveToContent() a nd tests if the
current content node is a start tag or
empty element tag.
(Inherited from XmlReader) IsStartElement(String) Calls MoveToContent() and tests if the
current content node is a start tag or
empty element tag and if the Name
property of the element found matches
the given argument.
(Inherited from XmlReader) IsStartElement(String, String) Calls MoveToContent( ) and tests if the
current content node is a start tag or
empty element tag and if the LocalName
and NamespaceURI properties of the
element found match the given strings.
(Inherited from XmlReader) Table 6 XmlReader Methods

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Working with XML 14.6 SUMMARY ● Extensible Markup Language (XML) is a markup language used to describe the content and structure of data in a document. ● It is a simplified version of Standard Generalized Markup Language (SGML). ● XML is an industry standard for delivering content on the Internet. Because it provides a facility to define new tags, XML is also extensible. ● Like HTML, XML uses tags to describe content. However, rather than focusing on the presentation of content, the tags in XML describe the meaning and hierarchical structure of data. This functionality allows for the sophisticated data types that are required for efficient data interchange between different programs and systems. Further, because XML enables separation of content and presentation, the content, or data, is portable across heterogeneous systems. 14.7 REFERENCE FOR FURTHER READING 1. Beginning ASP.NET 4.5 in C#, Matthew MacDonald, Apress(2012) 2. The Complete Reference ASP .NET, MacDonald, Tata McGraw Hill 3. Beginning ASP.NET 4 in C# and VB Imar Spanajaars, WROX 14.8 UNIT END EXERCISES 1. What is XML? Explain with examples. 2. What are the advantages of XML? 3. Explain the different types of XML Classes? 4. Write a short note on: a. XMLTextWriter b. XMLTextReader  munotes.in

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206 .Net technology 15 CACHING Unit Structure : 15.0 Objective 15.1 Introduction 15.2 When to Use Caching 15.3 Output Caching 15.4 Data Caching 15.5 Summary 15.6 Reference for further reading 15.7 Unit End Exercises 15.0 OBJECTIVE ● To understand the use of caching in .NET technologies. ● To study when to use caching. ● To learn the output and data catching techniques. 15.1 INTRODUCTION ● Caching is the technique of storing a memory copy of some information that’s costly to create. ● Example, cache the results of a complex query so that subsequent requests don’t need to access the database at all. Rather, they can snatch the appropriate object directly from server memory, a much faster proposition. ● The real picture of caching is that unlike many other performance enhancing techniques, caching bolsters both performance and scalability. ● Performance is better because the time taken to retrieve the information is cut down dramatically. ● Scalability is improved because you work around bottlenecks such as database connections. ● Server memory is a limited resource; if you try to store too much, some of that information will be paged to disk, potentially slowing down the entire system. That’s why the best coaching strategies are self-limiting. munotes.in

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Caching ● When we store information in a cache, we expect to find it there on a future request most of the time. However, the lifetime of that information is at the discretion of the server. ● If the cache becomes full or other applications consume a large amount of memory, information will be selectively evicted from the cache, ensuring that performance is maintained. It’s this self-sufficiency that makes caching so powerful. ● Cache can be completely rendered HTML for a page, a portion of that HTML, or arbitrary objects. We can customize expiration policies and set up dependencies so that items are automatically removed when other resources such as files or database tables are modified. 15.2 WHEN TO USE CACHING ● Caches are usually used to keep track of persistent responses to user requests. ● It can also be used in the case of storing results of long computational operations. ● Caching is storing data in a location different from the main data source such that it’s faster to access the data. Like load balancers, caching can be used in various places of the system. ● Caching is done to avoid redoing the same complex computation repeatedly. ● Caching is used to improve the time complexity of algorithms for example, say dynamic programming, the memorization technique to reduce time complexity. ● In the case of system design concepts, caching as a concept is also the same. ● Caching is used to improve the speed of a system. ● To improve the latency of a system, we need to use caching. ● To reduce network requests can also be a cause for using caching. ● Caching provides a twofold, threefold, or even tenfold performance improvement by retaining important data for just a short period of time. ● ASP.NET really has two types of caching: ○ Output caching: ■ This is the simplest type of caching. ■ It stores a copy of the final rendered HTML page that is sent to the client. The next client that submits a request munotes.in

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208 .Net technology for this page doesn’t actually run the page. Instead, the final HTML output is sent automatically. ■ The time that would have been required to run the page and its code is completely reclaimed. ○ Data caching: ■ This type of caching is carried out manually in code. ■ To use data caching, we store important pieces of information that are time consuming to reconstruct in the cache. Other pages can check for the existence of this information and use it, thereby bypassing the steps ordinarily required to retrieve it. ■ Data caching is conceptually the same as using application state, but it’s much more server-friendly because items will be removed from the cache automatically when it grows too large and performance could be affected. Items can also be set to expire automatically. ○ Fragment caching: ■ This is a specialized type of output caching instead of caching the HTML for the whole page, it allows you to cache the HTML for a portion of it. ■ Fragment caching works by storing the rendered HTML output of a user control on a page. ■ The next time the page is executed, the same page events fire, but the code for the appropriate user control is not executed. ○ Data source caching: ■ This is the caching that’s built into the data source controls, including the SqlDataSource, ObjectDataSource, and XmlDataSource. The data source caching uses data caching. ■ The difference is that you don’t need to handle the process explicitly. Instead, you simply configure the appropriate properties, and the data source control manages the caching storage and retrieval. 15.3 OUTPUT CACHING ● With this type of caching, the final rendered HTML of the page is cached. ● When the same page is requested again, the control objects are not created, the page life cycle doesn’t start, and none of your code executes. Instead, the cached HTML is served. Clearly, output munotes.in

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Caching caching gets the theoretical maximum performance increase, because all the overhead of your code is sidestepped. 1. Declarative Output Caching Example 1 : create a simple page that displays the current time of day. The code for this page is straightforward. It simply sets the date to appear in a label when the Page.Load event occurs: Example 1: protected void Page_Load(Object sender, EventArgs e)
{
lblDate. Text = "The time is now:
";
lblDate.Text += DateTime.Now.ToString();
} Two ways to add this page to the output cache. The most common approach is to insert the OutputCache directive at the top of your .aspx file, just below the Page directive shown in example 2: Example 2: <%@ OutputCache Duration="20" VaryByParam="None" %> 2. Caching and the Query String ● Caching is deciding when a page can be reused and when information must be accurate up to the latest second. Use caching to efficiently reuse slightly stale data without a problem, and with a considerable performance improvement. ● Occasionally information needs to be dynamic. One example is if the page uses information from the current user’s session to tailor the user interface. In this type, full page caching just isn’t suitable. Second example is if the page is receiving information from another page through the query string. ● ASP.NET provides options. We can set the VaryByParam attribute to * to indicate that the page uses the query string and to instruct ASP.NET to cache separate copies of the page for different query string arguments, as shown below: <%@ OutputCache Duration="20" VaryByParam="*" %> munotes.in

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210 .Net technology ● When requesting the page with additional query string information, ASP.NET will inspect the query string. If the string matches a previous request, and a cached copy of that page exists, it will be reused. ● To get a better idea how this process works, consider the following series of requests: 1. You request a page without any query string parameter and receive page copy A. 2. You request the page with the parameter ProductID=1. You receive page copy B. 3. Another user requests the page with the parameter ProductID=2. That user receives copy C. 4. Another user requests the page with ProductID=1. If the cached output B has not expired, it’s sent to the user. 5. The user then requests the page with no query string parameters. If copy A has not expired, it’s sent from the cache. Caching with Specific Query String Parameters ● Setting VaryByParam="*" allows you to use caching with dynamic pages that vary their output based on the query string. ● This approach could be extremely useful for a product detail page, which receives a product ID in its query string. With vary-by-parameter caching, you could store a separate page for each product, thereby saving a trip to the database. However, to gain performance benefits you might have to increase the cached output lifetime to several minutes or longer. ● Pages that accept a wide range of different query string parameters just are not suited to output caching. ● Setting VaryByParam to the wildcard asterisk (*) is unnecessarily vague. It’s usually better to specifically identify an important query string variable by name. example: <%@ OutputCache Duration="20" VaryByParam="ProductID" %> ● ASP.NET will examine the query string looking for the ProductID parameter. Requests with different ProductID parameters will be coached separately, but all other parameters will be ignored. This is particularly useful if the page may be passed additional query string information that it doesn’t use. ASP.NET has no way to distinguish the “important” query string parameters without your help. Specify several parameters, as long as you separate them with semicolons, as follows: <%@ OutputCache Duration="20" VaryByParam="ProductID;CurrencyType" %> munotes.in

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Caching In this case, the query string will cache separate versions, provided the query string differs by ProductID or CurrencyType. Custom Caching Control ● ASP.NET allows you to create your own procedure that decides whether to cache a new page version or reuse an existing one. ● This code examines whatever information is appropriate and then returns a string. ● ASP.NET uses this string to implement caching. If your code generates the same string for different requests, ASP.NET will reuse the cached page. ● If your code generates a new string value, ASP.NET will generate a new cached version and store it separately. ● One way you could use custom caching is to cache different versions of a page based on the browser type. ● The following example uses the name browser because pages will be cached based on the client browser: <%@ OutputCache Duration="10" VaryByParam="None" VaryByCustom="browser" %> ● To create the procedure that will generate the custom caching string. This procedure must be coded in the global.asax application file, as shown below example 3: Example 3 public override string GetVaryByCustomString(
HttpContext context, string arg)
{
// Check for the requested type of caching.
if (arg == "browser")
{
// Determi ne the current browser.
string browserName;
browserName = Context.Request.Browser.Browser;
browserName +=
Context.Request.Browser.MajorVersion.ToString();
// Indicate that this string should be used to vary caching.
return browserName;
}
else
{
return base.GetVaryByCustomString(context, arg);
}
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212 .Net technology ● The GetVaryByCustomString() function passes the VaryByCustom name in the arg parameter. This allows you to create an application that implements several types of custom caching in the same function. Each different type would use a different VaryByCustom name (such as Browser, BrowserVersion, or DayOfWeek). Your GetVaryByCustomString() function would examine the VaryByCustom name and then return the appropriate caching string. If the caching strings for different requests match, ASP.NET will reuse the cached copy of the page. ● The OutputCache directive also has a third attribute that you can use to define caching. This attribute, VaryByHeader, allows you to store separate versions of a page based on the value of an HTTP header received with the request. You can specify a single header or a list of headers separated by semicolons. ● We can use this technique with multilingual sites to cache different versions of a page based on the client browser language, as follows: <%@ OutputCache Duration="20" VaryByParam="None" VaryByHeader="Accept-Language" %> Caching with the HttpCachePolicy Class ● Cache property, which provides an instance of the System.Web.HttpCachePolicy class. ● This object provides properties that allow you to turn on caching for the current page. ● This allows you to decide programmatically whether you want to enable output caching. ● Example 4 shows, the date page has been rewritten so that it automatically enables caching when the page is first loaded. This code enables caching with the SetCacheability() method, which specifies that the page will be cached on the server and that any other client can use the cached copy of the page. The SetExpires() method defines the expiration date for the page, which is set to be the current time plus 60 seconds. Example 4 protected void Page_Load (Object sender, EventArgs e)
{
// Cache this page on the server.
Response.Cache.SetCacheability(HttpCacheability.Public);
// Use the cached copy of this page for the next 60 seconds.
Response.Cache.SetExpires(DateTime.Now.AddSeconds(60));
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Caching // invalidate the page when the user clicks the Refresh button
// (which some rogue browsers attempt to do).
Response.Cache.SetValidUntilExpires(true);
lblDate.Text = "The time is now:
" +
DateTime.Now.ToString();
} Post-Cache Substitution and Fragment Caching ● Fragment caching: ○ In this case, you identify just the content you want to cache, wrap that in a dedicated user control, and cache just the output from that control. ● Post-cache substitution: ○ In this case, you identify just the dynamic content you don’t want to cache. You then replace this content with something else using the Substitution control. ● Fragment caching is the easiest to implement. ● If you have a small, distinct portion of content to cache, fragment caching makes the most sense. ● Conversely, if you have only a small bit of dynamic content, post-cache substitution may be the more straightforward approach. Both approaches offer similar performance shown in below example 5. Example 5 private static string GetDate(HttpContext context)
{
return "" + DateTime.Now.ToString() + "";
}
To get this in the page, you need to use the
Response.WriteSubstitution() method at some point:
protected void Page _Load(object sender, EventArgs e)
{
Response.Write("This date is cached with the page: ");
Response.Write(DateTime.Now.ToString() + "
");
Response.Write("This date is not: ");
Response.WriteSubstitution(new
HttpResponseSubstitutionCallback(GetDate));
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214 .Net technology 15.4 DATA CACHING ● Data caching is the most flexible type of caching, but it also forces you to take specific additional steps in your code to implement it. ● The basic principle of data caching is that you add items that are expensive to create a special built-in collection object (called Cache). ● This object works much like the Application object. It’s globally available to all requests from all clients in the application. However, a few key differences exist: ○ The Cache object is thread-safe: This means you don’t need to explicitly lock or unlock the Cache collection before adding or removing an item. ○ Items in the cache are removed automatically: ASP.NET will remove an item if it expires, if one of the objects or files it depends on is changed, or if the server becomes low on memory. This means you can freely use the cache without worrying about wasting valuable server memory, because ASP.NET will remove items as needed. But because items in the cache can be removed, you always need to check if a cached object exists before you attempt to use it. Otherwise, you’ll run into a NullReferenceException. ○ Items in the cache support dependencies: We can link a cached object to a file, a database table, or another type of resource. If this resource changes, your cached object is automatically deemed invalid and released. ○ Adding Items to the Cache As with the Application and Session collections, you can add an item to the Cache collection just by assigning a new key name: Cache["key"] = item; ○ A better approach is to use the Cache.Insert() method. Table 1 below lists the four versions of the Insert() method. Overload Description Cache.Insert(key,
value) Inserts an item into the cache under the
specified key name, using the default priority
and expiration. This is the same as using the
indexer - based collection syntax and assigning
to a new key name. Cache.Insert(key, value,
dependencies)
Inserts an item into the cache under the
specified key name, using the default priority
and e xpiration. The last parameter contains a
CacheDependency object that links to other
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Caching Overload Description item to be invalidated when these change. Cache.Insert(key, value,
dependencies,
absoluteExpiration,
slidingExpiration) Inserts an item into the cache under the
specified key name, using the default priority
and the indicated sliding or absolute expiration
policy. This is the most commonly used
version of the Insert() method. Cache.Insert(key, value,
dependencies,
absolute Expiration,
slidingExpiration,
priority,
onRemoveCallback) Allows you to configure every aspect of the
cache policy for the item, including expiration,
priority, and dependencies. In addition, you
can submit a delegate that points to a method
you want inv oked when the
item is removed. Table 1 Insert Methods Example that stores an item with a sliding expiration policy of 10 minutes, with no dependencies: Cache.Insert("MyItem", obj, null, DateTime.MaxValue, TimeSpan.FromMinutes(10)); A Simple Cache Test The following Example 6 presents a simple caching test. An item is cached for 30 seconds and reused for requests in that time. Example 6: protected void Page_Load(Object sender, EventArgs e)
{
if (this.IsPostBack)
{
lblInfo.Text += "Page posted back.
";
}
else
{
lblInfo.Text += "Page created.
";
}
DateTime? testItem = (DateTime?)Cache["TestItem"];
if (testItem == null)
{
lblInfo.Text += "Creating TestItem...
";
testItem = DateTime.Now;
lblInfo.Text += "Storing Test Item in cache ";
lblInfo.Text += "for 30 seconds.
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216 .Net technology Cache.Insert("TestItem", testItem, null,
DateTime.Now.AddSeconds(30), TimeSpan.Zero);
}
else
{
lblInfo.Text += "Retrieving TestItem...
";
lblInfo.Text += "TestItem is '" + testItem.ToString();
lblInfo.Text += "'
";
}
lblInfo.Text += "
";
}
Cache Priorities ● Setting a priority while adding an item to the cache. The priority only has an effect if ASP.NET needs to perform cache searches, which is the process of removing cached items early because memory is becoming scarce. ● To assign a cache priority, choose a value from the CacheItemPriority enumeration shown in table 2. Lists of all the value: Value Description High These items are the least likely to be deleted from
the cache as the server frees system memory. AboveNormal These items are less likely to be deleted than
Normal priority items. Normal These items have the default priority level. They
are deleted only after Low or BelowNormal
priority items have been removed. BelowNormal These items are more likely to be deleted than
Normal priority items. Low These items are the most likely to be deleted from
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Caching the cache as the server frees system memory. NotRemovable These items will ordinarily not be deleted from the
cache as the server frees system memory. Table 2 Cache properties value Caching with the Data Source Controls ● The SqlDataSource, ObjectDataSource, and XmlDataSource all support built-in data caching. ● Using caching with these controls is highly recommended, because the data source controls often generate extra query requests. ● For example, they requery after every postback when parameters change, and they perform a separate query for every bound control, even if those controls use exactly the same command, Even a little caching can reduce this overhead. To support caching, the data source controls all use the same properties, which are listed below Cache-Related Properties of the Data Source Controls shown in table 3 Property Description EnableCaching If true, caching is switched on. It’s false by
default. CacheExpirationPolicy Uses a value from the
DataSourceCacheExpiry enumeration —
Absolute for absolute expiration (which
times out after a fixed interval
of time) or Sliding for sliding expiration
(which resets the time
window every time the data object is
retrieved from the cache). CacheDuration The number of seconds to cache the data
object. If you are using
sliding expiration, the time limit is reset
every time the object is
retrieved from the cache. The default value,
0 (or Infinite), keeps
cached items perpetually. CacheKeyDependency and
SqlCacheDependency
Allows you to make a cached item
dependent on ano ther item in the
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218 .Net technology table in your database
(SqlCacheDependency). Dependencies are
discussed in the “Cache
Dependencies” section. Table 3 Cache -Related Properties 15.5 SUMMARY ● Caching is the technique of storing a memory copy of some information that’s costly to create. ● Caches are usually used to keep track of persistent responses to user requests. ● Caching provides a twofold, threefold, or even tenfold performance improvement by retaining important data for just a short period of time. ● Data caching is the most flexible type of caching, but it also forces you to take specific additional steps in your code to implement it. ● Setting a priority while adding an item to the cache. 15.6 REFERENCE FOR FURTHER READING 1. Beginning ASP.NET 4.5 in C#, Matthew MacDonald, Apress(2012) 2. The Complete Reference ASP .NET, MacDonald, Tata McGraw Hill 3. Beginning ASP.NET 4 in C# and VB Imar Spanajaars, WROX 15.7 UNIT END EXERCISES 1. What is caching? When to Use Caching? 2. Explain Output Caching with an example? 3. What is Data Caching? Explain a few key differences? 4. Write a short note on custom caching control?  munotes.in

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219 16 LINQ Unit Structure : 16.0 Objective 16.1 Introduction 16.2 Understanding LINQ 16.3 LINQ Basics 16.4 Summary 16.5 Reference for further reading 16.6 Unit End Exercises 16.0 OBJECTIVE ● This chapter would make you understand the following concepts: ○ LINQ ○ LINQ operators ○ Data model to an object model ○ LINQ queries ● The learner can use LINQ to query multiple data sources. ● The learners can learn different LINQ operator concept to write different queries against different databases. ● Learners can use the same basic query expression patterns to query and transform data into SQL databases, ADO.NET datasets, XML documents, and .NET collections and flows. 16.1 INTRODUCTION ● The data required for an application can be stored in a relational database, business objects, XML file, or on web services. ● Retrieving in memory objects is simple and less expensive than retrieving data from a database or XML file. The data accessed are not used directly. It required ordering, grouping and altering. ● LINQ allows joining data from different data sources and executing set data processing operations in a few lines of code. It defines a common syntax and a programming model to query different types of data sources using a common language. ● LINQ is a deeply integrated part of .NET and the C# language. it can be used equally well in any type of .NET application, most likely to use LINQ as part of a database component. we can use LINQ in addition to ADO.NET data access code. munotes.in

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220 .Net technology Advantages of LINQ ● Familiar language: Developers don't have to learn a new query language for each type of data source or data format. ● Less coding: It reduces the amount of code to be written as compared with a more traditional approach. ● Readable code: LINQ makes the code more readable so other developers can easily understand and maintain it. ● Standardized way of querying multiple data sources: The same LINQ syntax can be used to query multiple data sources. ● Compile time safety of queries: It provides type checking of objects at compile time. ● IntelliSense Support: LINQ provides IntelliSense for generic collections. ● Shaping data: You can retrieve data in different shapes. Disadvantages of LINQ are: ● With the use of LINQ, it's very difficult to write a complex query like SQL. ● It was written in the code, and we cannot make use of the Cache Execution plan, which is the SQL feature as we do in the stored procedure. ● If the query is not written correctly, then the performance will be degraded. ● If we make some changes to our queries, then we need to recompile the application and need to redeploy the dll to the server. 16.2 UNDERSTANDING LINQ Operators: ● A set of extension methods forming a query pattern is known as LINQ Standard Query Operators. As building blocks of LINQ query expressions, these operators offer a range of query capabilities like filtering, sorting, projection, aggregation, etc. LINQ standard query operators can be categorized into the following ones on the basis of their Functionality. Shown in Table 1.

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LINQ
Table 1 List of Operators Implementations: LINQ includes three basic types of implementation a. LINQ to objects: It used to query almost any kind of collections that exists in the .NET Framework. b. LINQ to XML: It used to query XML data directly in your web application c. LINQ to ADO.NET: It used to access data from SQL Server and many other different kinds of data sources. Using LINQ to ADO.NET you can perform LINQ to DataSet, LINQ to SQL, and LINQ to Entities. LINQ to SQL allows writing object-oriented queries against SQL Server databases. LINQ to DataSet allows writing queries against the DataSet. LINQ to Entities allows writing queries against the ADO.net Entity framework. 16.3 LINQ BASICS LINQ includes three basic types of implementation a. LINQ to objects: It used to query almost any kind of collections that exist in the .NET Framework. b. LINQ to XML: It used to query XML data directly in your web application c. LINQ to ADO.NET: It used to access data from SQL Server and many other different kinds of data sources. Using LINQ to ADO.NET you can perform LINQ to DataSet, LINQ to SQL, and LINQ to Entities. LINQ to SQL allows writing object-oriented
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222 .Net technology queries against SQL Server databases. LINQ to DataSet allows writing queries against the DataSet. LINQ to Entities allows writing queries against the ADO.net Entity framework. Mapping Your Data Model To An Object Model Using LINQ to Objects ● The term LINQ to Objects refers to the use of LINQ queries to access in memory data structures. Query any type that supports IEnumerable. ● This means that you can use LINQ queries not only with user-defined lists, arrays, dictionaries, and so on, but also in conjunction with .NET Framework APIs that return collections. ● For example, The System.Reflection classes return information about types stored in a specified assembly, and then filter those results using LINQ. ● LINQ queries offer three main advantages over traditional foreach loops: ○ They are more concise and readable, especially when filtering multiple conditions. ○ They provide powerful filtering, ordering, and grouping capabilities with a minimum of application code. ○ They can be ported to other data sources with little or no modification. LINQ to XML: Provides creation and manipulation of XML documents using the same syntax and general query mechanism as the other LINQ variety shown in example 1. Example 1: LINQ to create XML files to store student details. Code:
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Xml.Linq;
namespace ConsoleApplication1
{
class Program
{ munotes.in

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LINQ static void Main(string[] args)
{
XDocument xdoc = new XDocument(
new XElement("students",
new XElement("student",
new XAttribute("ID", "1"),
new XAttribute("City", "Mumbai"),
new XAttribute("Region", "North Mumbai"),
new XElement("course",
new XAttribute( "Item", "Web progamming"),
new XAttribute("Price", 1000)
),
new XElement("course",
new XAttribute("Item", "Java"),
new XAttribute("Price", 2000)
)
),
new XElement("student",
new XAttribute("ID", "2"),
new XAttribute("City", "Mumbai"),
new XAttribute("Region", "South Mumbai"),
new XElement("course",
new XAttribute("Item", "ADO.NET"),
new XAttribute("Price", 5000)
)
)
)
);
Console.WriteLine(xdoc);
Console.Write("Program finished, press Enter/Return to
continue:");
Console.ReadLine();
}
}
}
Output: munotes.in

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224 .Net technology
LINQ to ADO.net ● LINQ to ADO.Net means using the LINQ queries on the objects in the ADO.Net. ● The LINQ to ADO.Net gives us a chance to write the LINQ Queries on Enumerable objects in ADO.Net and the LINQ to ADO.Net is having the three types of LINQ technologies available. ● These are LINQ to Dataset, LINQ to SQL and LINQ to Entities. LINQ Works ● To use LINQ, you create a LINQ expression. ● The return value of a LINQ expression is an iterator object that implements IEnumerable. ● When you enumerate over the iterator object, LINQ performs its work. ● There are three separate ADO.NET Language-Integrated Query (LINQ) technologies: ○ LINQ to DataSet ○ LINQ to SQL, and ○ LINQ to Entities. ○ LINQ to DataSet provides richer, optimized querying over the DataSet and LINQ to SQL enables you to directly query SQL Server database schemas, and LINQ to Entities allows you to query an Entity Data Model. ● The following figure 1 provides an overview of how the ADO.NET LINQ technologies relate to high-level programming languages and LINQ-enabled data sources.
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LINQ
Figure 1. ADO.NET LINQ technologies LINQ to DataSet ● The DataSet is a key element of the disconnected programming model that ADO.NET is built on, and is widely used. ● LINQ to DataSet enables developers to build richer query capabilities into DataSet by using the same query formulation mechanism that is available for many other data sources. LINQ to SQL ● LINQ to SQL is a useful tool for developers who do not require mapping to a conceptual model. ● By using LINQ to SQL, use the LINQ programming model directly over existing database schema. ● LINQ to SQL enables developers to generate .NET Framework classes that represent data. Rather than mapping to a conceptual data model, these generated classes map directly to database tables, views, stored procedures, and user-defined functions. LINQ to Entities ● Most applications are currently written on top of relational databases. At some point, these applications will need to interact with the data represented in a relational form. ● Database schemas are not always ideal for building applications, and the conceptual models of application are not the same as the logical models of databases. ● The Entity Data Model is a conceptual data model that can be used to model the data of a particular domain so that applications can interact with data as objects. For more information, see ADO.NET Entity Framework.
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226 .Net technology Aggregate functions (shown in example 2) Aggregate functions are extension methods in LINQ. The following are the Aggregate functions. ● Average(): It is used to average the number of elements in the list or collection. ● Count(): COUNT () function in LINQ is used to count the number of elements in the list or collection. ● Max(): Max () function in LINQ is used to return the maximum value from the collection. ● Min(): MIN () function of LINQ is useful to get the minimum value from a collection or list. ● Sum(): In LINQ sum() function is used to calculate the sum of the items in collections or lists. ● Aggregate: Aggregate() function is used to perform the operation on each item of the list. The Aggregate() function performs the action on the first and second elements and then carries forward the result. Example 2: LINQ with Aggregate functions. using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Xml.Linq;
namespace ConsoleApplication1
{
class Program
{
static void Main(string[] args)
{
int[] n = { 1,2,3,4,5,6,7,8,9,10 };
Console.WriteLine(" Total count = " + n.Count());
Console.WriteLine("Average = " + n.Average());
Console.WriteLine("Summation = " + n.Sum());
Console.WriteLine("Max value = " + n.Max());
Console.WriteLine("Min Value = " + n.Min());
Console.WriteLine("Aggregate Value = " + n.A ggregate((a, b) =>
a + b));
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LINQ }
}
}
Output:
LINQ Sorting Operators (Shown in Example 3) ● Sorting Operators in LINQ are used to change the order or sequence of the data (either ascending or descending), which is based on one or more attributes. ○ OrderBy: This operator will sort the values in ascending order. ○ OrderByDescending: This operator will sort the values in descending order. ○ ThenBy: This operator is used to perform the secondary sorting in ascending order. ○ ThenByDescending: This operator is used to perform the sorting in descending order. ○ Reverse: This operator is used to reverse the order of elements in the collection. Example 3: LINQ to sort employee list by employee name in descending order. Code:
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Xml.Linq;
namespace ConsoleApplication1
{
class Employee
{
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228 .Net technology public int EmployeeID { get; set; }
public string EmpName { get; set; }
public int Age { get; set; }
}
class Program
{
static void Main(string[] args)
{
List empList = new List()
{
new Employee() { EmployeeID = 1, EmpName = "Pallavi", Age = 28 } ,
new Employee() { EmployeeID = 2, EmpName = "Kimaya", Age = 26 } ,
new Employee() { EmployeeID = 3, EmpName = "Dev", Age = 35 } ,
new Employee() { EmployeeID = 4, EmpName = "Ram" , Age = 25 } ,
new Employee() { EmployeeID = 5, EmpName = "Sonal" , Age = 28 }
};
var empResult = empList.OrderByDescending(x => x.EmpName);
foreach (var emp in empResult)
{
Console.WriteLine(emp.EmpName);
}
Console.ReadLine();
}
}
}
Output:
LINQ SET OPERATORS LINQ provides standard set operators such as Except, Intersect, Union, and Distinct. These operators behave in the same way as in DBMS. ● Union operator : This operator requires two collections of items. After applying union operator, you will get a new collection. It removes the duplicate entries. ● Intersect operator : This operator provides the common elements in both lists.
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LINQ ● Except operator : Except the operator provides the element only from the first list. The new list does not contain common elements. Shown in example 4.
Example 4: LINQ with set operators. Code:
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Xml.Linq;
namespace ConsoleApplication1
{
class Program
{
static void Main(string[] args)
{
int[] List1 = {1,2,3,4,5,6 };
int[] List2 = {2,3,5};
Console.WriteLine("Unique elements in both list \n");
var result = List1.Union(List2);
foreach (int i in result)
{
Console.WriteLine(i);
}
Console.WriteLine(" \n Common elements in both list \n\n");
var IntResult = List1.Intersect(List2);
foreach (in t i in IntResult)
{
Console.WriteLine(i);
}
Console.WriteLine(" \n Element in list1 after minus from list2 \n");
var ExceptResult = List1.Except(List2);
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230 .Net technology foreach (int i in ExceptResult)
{
Console.WriteLine(i);
}
Console.WriteLine ("\n Element in list1 after disctinct \n");
var r = List1.Distinct();
foreach (int i in r)
{
Console.WriteLine(i);
}
Console.ReadLine();
}
}
}
Output:
LINQ Partition Operator In LINQ, Partition Operators are used to partition the list/collections items into two parts and return one part of the list items. Here are the different types of partitioning operators available in LINQ ● TAKE: This operator is used to return the specified number of elements in the sequence.
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LINQ ● TAKEWHILE: This operator is used to return the elements in the sequence which satisfy the specific condition. ● SKIP: This operator is used to skip the specified number of elements in a sequence and return the remaining elements. ● SKIPWHILE: This operator is used to skip the elements in a sequence based on the condition, which is defined as true. Quantifier Operators ● “All” operator checks whether all elements in the list satisfies the specified condition or not. It returns true if all the elements satisfy a condition otherwise it returns false. ● “Any” operator checks whether any element in the list satisfies the given condition or not. It returns true if any element satisfies the given condition. As it name indicates ● “Contains” operator checks whether a particular element exists in the collection or not. It also returns true or false. It returns true if any element is available in the given list. LINQ Element Operators In LINQ, element operators are used to return the first and last element of the list or single element from the collection or a specific element based on the index value from the collection. By using these element operators, we can get the list/collection of items at the specific position. ● First: It returns the first element in sequence or from the collection based on the condition. ● FirstOrDefault: It is the same as First, but it returns the default value in case when no element is found in the collection. ● Last: It returns the last element in sequence or the last element based on the matching criteria. ● ElementAt: It returns an element from the list based on the specific index position. ● ElementAtOrDefault: It is the same as ElementAt, but it returns the default value in case no element is present at the specified index of the collection. ● Single: It returns the single specific element from the collection. ● SingleOrDefault: It is the same as Single, but it returns the default value in case if no element is found in the collection. ● DefaultifEmpty: It returns the default value in case if the list or collection contains empty or null values. munotes.in

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232 .Net technology 16.4 SUMMARY ● LINQ functionality can be achieved by importing the System.Linq namespace in our application. ● Generally, the LINQ contains a set of extension methods which allows us to query the source of data objects directly in our code based on the requirement. ● In LINQ we have learnt LINQ introduction, syntax, min function, max function, sum function, count function, sorting operators and how it helps in timesaving. ● Ultimately, you have known about how language integrated queries can be used for several types of data sources. 16.5 REFERENCE FOR FURTHER READING 1. Beginning Visual C# 2012 Programming, Karli Watson, Jacob Vibe Hammer, Jon D. Reid, Morgan Skinner, Daniel Kemper, Christian Nagel,ISBN: 978-1-118-31441-8,Wrox Publication 2. Professional C# 2008,Christian Nagel, Bill Evjen, Jay Glynn, Karli Watson, Morgan Skinner,ISBN: 978-1-118-64321-1 ,Wrox Publication 3. Murach’s C# 2015,Anne Boehm and Joel Murach, ISBN 978-1- 890774-94-3,Murrach Books 16.6 UNIT END EXERCISES 1. Explain LINQ with examples. 2. Explain different types of LINQ operators. 3. What are the different ways to implement LINQ? 4. What are the steps for creating LINQ to objects? 5. What are the steps for creating LINQ to XML? 6. What are the Advantages and Disadvantages of LINQ?  munotes.in

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233 17 ASP.NET AJAX Unit Structure : 17.0 Objective 17.1 Introduction 17.2 ScriptManager 17.3 Partial Refreshes 17.4 Progress Notification 17.5 Timed Refreshes 17.6 Summary 17.7 Reference for further reading 17.8 Unit End Exercises 17.0 OBJECTIVE ● To understand the use ASP.NET AJAX toolkit. ● To use several features of AJAX in ASP.NET. ● To learn how to use it to create the next generation of highly interactive, dynamic web pages. 17.1 INTRODUCTION ● ASP.NET AJAX consists of two key parts: a client-side portion and a server-side portion. ○ The client-side portion is a set of JavaScript libraries. ○ non-ASP.NET developers can use them in their own web pages. ○ The client libraries don’t expose much in the way of features. Rather, they establish a basic foundation you can use to develop ASP.NET AJAX pages. ○ This foundation extends the JavaScript language to fill in a few of its gaps, and provides some basic infrastructure. ○ The server-side portion of ASP.NET AJAX works at a higher level. ○ It includes controls and components that use the client-side JavaScript libraries. For example, a web form that contains the DragPanel component gives users the ability to drag a panel around in the browser window. munotes.in

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234 .Net technology ○ JavaScript uses the client-side ASP.NET AJAX libraries. However, the DragPanel renders all the JavaScript code it needs. ● ASP.NET AJAX is the start of a new direction in ASP.NET development. Before going any further, it’s worth getting an overview of all the features that ASP.NET AJAX provides. ● List of analysis: ○ JavaScript language extensions: These extensions make JavaScript work a little more like a modern object-oriented language, with support for namespaces, inheritance, interfaces, enumerations, and reflection. ○ Remote method calls: ASP.NET AJAX pages can call web services that you design. This feature allows users to get information from the server without performing a full-page postback. ○ ASP.NET services: This feature allows you to call the server to use one of two ASP.NET services one that uses forms authentication information and one that gets data from the current user profile. ○ Partial page refreshes: The new UpdatePanel control gives you a way to define a portion of a page that will be updated without requiring a full-page postback. ○ Prebuilt controls: The popular ASP.NET AJAX Control Toolkit is stocked with more than 30 controls and control extenders that use ASP.NET AJAX to great effect. They allow you to make controls collapse and expand, add dynamic animations, and support autocompletion and drag-and-drop. And once again, these classes handle the low-level JavaScripts. ASP.NET AJAX on the Client: The Script Libraries ● The client-side portion of ASP.NET AJAX relies on a small collection of JavaScript files. There are two ways to deploy the ASP.NET AJAX script files. If you build an ASP.NET application, they’re available through the System.Web.Extensions.dll assembly and served out on demand. ● In ASP.NET, you won’t find individual JavaScript files for the client libraries. Instead, the client libraries are embedded in the System.Web.Extensions.dll assembly and served up as a script resource. Script resources allow you to map a URL to a resource that’s embedded in an assembly. ● For example, example 2 shows a sample script block that extracts the ASP.NET AJAX script library: munotes.in

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ASP.NET AJAX Example 2: ASP.NET includes a script resource handler that responds to these requests. It examines the passed- in query string argument and returns the requested script file. ASP.NET AJAX on the Server: The ScriptManager ● To type long URLs there is no need to script resources on every page that requires ASP.NET AJAX. The solution is to use an ASP.NET control called the ScriptManager. ● The ScriptManager is the brains of the server-side ASP.NET AJAX model. It’s a web control that doesn’t have any visual appearance on the page. ● It performs a key task: it renders the links to the ASP.NET AJAX JavaScript libraries. ● To add the ScriptManager to a page, you can drag it from the AJAX Extensions tab of the Toolbox. ScriptManager is declared in the .aspx file: ● Each page that uses ASP.NET AJAX features requires an instance of the ScriptManager. ● Allows only one ScriptManager on a page. Along with rendering the links for the ASP.NET AJAX client libraries, the ScriptManager also performs several other important tasks. ● It can render references to other script files, create proxies that enable it to call web services asynchronously from the browser, and manage the way UpdatePanel controls refresh their content. munotes.in

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236 .Net technology 17.2 SCRIPTMANAGER ● Manages ASP.NET Ajax script libraries and script files, partial-page rendering, and client proxy class generation for Web and application services. Namespace: System.Web.UI Assembly: System.Web.Extensions.dll [System.Drawing.ToolboxBitmap(typeof(EmbeddedResourceFinder), "System.Web.Resources.ScriptManager.bmp")] public class ScriptManager : System.Web.UI.Control, System.Web.UI.IPostBackDataHandler, System.Web.UI.IPostBackEventHandler The following examples show different scenarios for using the ScriptManager control. Enabling Partial-Page Updates ● Example 3: a Calendar and a DropDownList control are inside an UpdatePanel control. By default, the value of the UpdateMode property is Always, and the value of the ChildrenAsTriggers property is true. Therefore, child controls of the panel cause an asynchronous postback. Example 3: <%@ Page Language="C#" %>
Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1 -transitional.dtd">

runat="server" />
runat="server">

ShowTitle="True"

OnSelectionChanged="Calendar1_SelectionChanged"
runat="server" />

Background:


AutoPostBack="True"

OnSelectedIndexChanged="DropDownSelection_Change"
runat="ser ver">

White

Silver

Dark Gray

Khak i
D
ark Khaki

Selected date:

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238 .Net technology runat="server">None.

Handling Partial-Page Update Errors and Registering Script ● This provides custom error handling during partial-page updates. ● By default, when an error occurs during partial-page updates, a JavaScript message box is displayed. ● This example shows how to use custom error handling by providing a handler for the AsyncPostBackError event, and by setting the AsyncPostBackErrorMessage property in the event handler. ● We can set the AllowCustomErrorsRedirect property to specify how the custom errors section of the Web.config file is used when an error occurs during partial-page updates. ● In this example 4, the default value of the AllowCustomErrorsRedirect property is used. This means that if the Web.config file contains a customErrors element, that element determines how errors are displayed. Example 4: <%@ Page Language="C#" %>
Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1 -
transitional.dtd">

OnAsyncPostBackError="ScriptManager1_AsyncPostB ackError"
runat="server" >






Width="39px">
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ASP.NET AJAX Width="39px">
=


OnClick="Button1_Click" Text="calculate" />

runat="server" onclick="ClearErr orState()" />

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242 .Net technology

EnableScriptGlobalization="true" runat="server">


ChildrenAsTriggers="False" UpdateMode="Conditional">











17.3 PARTIAL REFRESHES ● Perhaps the most visible feature of the ASP.NET AJAX Extensions is the ability to do a partial or incremental page update without doing a full postback to the server, with no code changes and minimal markup changes. ● The advantages are extensive: the state of your multimedia (such as Adobe Flash or Windows Media) is unchanged, bandwidth costs are munotes.in

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ASP.NET AJAX reduced, and the client does not experience the flicker usually associated with a postback. ● The ability to integrate partial page rendering is integrated into ASP.NET with minimum changes into your project. ● One of the most fascinating controls in the ASP.NET AJAX framework is the UpdatePanel. This new control replaces the need for a page to refresh during a postback. Only portions of a page, designated by the UpdatePanel, are updated. ● This technique is known as partial-page rendering and can be highly effective in improving the user experience. 17.4 PROGRESS NOTIFICATION 1. Showing a Simulated Progress Bar • When adding the UpdateProgress control to a page, we get the ability to specify some content that will appear as soon as an asynchronous request is started and disappear as soon as the request is finished. ● This content can include a fixed message, but many people prefer to use an animated GIF, because it more clearly suggests that the page is still at work. ● The top figure shows the page as it first appears, with a straightforward UpdatePanel control containing a button. When the button is clicked, the asynchronous callback process begins. At this point, the contents of the UpdateProgress control appear underneath. ● The markup for this page defines an UpdatePanel followed by an UpdateProgress example 6 shown below: Example 6:

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● Depending on the layout we want, we can place our UpdateProgress control somewhere inside our UpdatePanel control. ● The UpdateProgress control only shows its content while the asynchronous callback is under way, it only makes sense to use it with an operation that takes time. Otherwise, the UpdateProgress will only show its ProgressTemplate for a few fractions of a second. ● To simulate a slow process, add a line to delay your code 10 seconds, as example 7 shown below: Example 7: Protected Sub cmdRefreshTime_Click(ByVal sender As Object, _
ByVal e As EventArgs) Handles cmdRefreshTime.Click

System.Threading.Thread.Sleep(TimeSpan.FromS econds(10))
lblTime.Text = DateTime.Now.ToLongTimeString()
End Sub 2. Cancellation ● The UpdateProgress control supports one other detail: a cancel button. When the user clicks a cancel button, the asynchronous callback will be cancelled immediately, the UpdateProgress content will disappear, and the page will revert to its original state. ● Adding a cancel button is a two-step process. First you need to add a fairly intimidating block of JavaScript code, which you can copy verbatim. You should place this code at the end of your page, after all your content but just before the end tag. Here’s the example 8 shows the need, in its rightful place: Example 8: <%@ Page Language="VB" AutoEventWireup="false"
CodeFile="WaitIndicator.aspx.vb"
Inherits="WaitIndicator" %>
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ASP.NET AJAX
...

...

● Once you’ve added this code, you can use JavaScript code to call its AbortPostBack() function at any time and cancel the callback. ● The easiest way to do this is to connect a JavaScript event to the AbortPostBack() function using a JavaScript event attribute. Add a JavaScript event attribute to virtually any HTML element. For example, you can deal with client-side clicks using the onclick attribute. Here’s a basic HTML button that uses this technique to connect itself to the AbortPostBack() function: ● If you click this Cancel button, the client-side AbortPostBack() function will be triggered and the callback will be cancelled immediately. Typically, this button in the ProgressTemplate of the UpdateProgress control, as shown in Figure 1. munotes.in

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Figure 1 ProgressTemplate 17.5 TIMED REFRESHES ● ASP.NET AJAX includes a Timer control that can help you implement a page that includes a stock ticker, and want to refresh this ticker periodically (say, every 5 minutes) to ensure it doesn’t become drastically outdated. ● The Timer control is refreshingly straightforward. You simply add it to a page and set its Interval property to the maximum number of milliseconds that should elapse before an update. ● For example 9 & 10, if you set Interval to 60000, the timer will force a postback after one minute elapses. ● If the Timer is in an UpdatePanel, it will trigger an asynchronous postback. If it’s not, and it’s not linked to an UpdatePanel with a trigger, the Timer will trigger an ordinary full-page postback. ● The timer raises a server-side Tick event, which you can handle to update your page. ● The timer is particularly well suited to pages that use partial rendering. That's because a refresh in a partially rendered page might just need to change a single portion of the page. ● To use the timer with partial rendering, wrap the updateable portions of the page in UpdatePanel controls with the UpdateMode set to Conditional, and add a trigger that forces an update whenever the timer fires:
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ASP.NET AJAX Example 9: UpdateMode="Conditional">

...





OnTick="Timer1_Tick" /> ● To stop the timer, simply need to set the Enabled property to false in server-side code. For example, following code show how to disable the timer after ten updates: Example 10: protected void Timer1_Tick(object sender, EventArgs e)
{
// Update the tick count and store it in view state.
int tickCo unt = 0;
if (ViewState["TickCount"] != null)
{
tickCount = (int)ViewState["TickCount"];
}
tickCount++;
ViewState["TickCount"] = tickCount;
// Decide whether to disable the timer.
if (tickCount > 10)
{
Timer1.Enabled = false;
}
} munotes.in

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248 .Net technology 17.6 SUMMARY ● The most exciting feature of ASP.NET AJAX is that it isn’t just another JavaScript library or a simple .NET component that simplifies callbacks. ● You can write your own JavaScript code that calls server-side functionality. ● We can keep using ordinary ASP.NET server controls but extend them with ASP.NET AJAX-fortified ingredients such as the UpdatePanel, or use the snazzy controls and control extenders that are included with the ASP.NET AJAX Control Toolkit. ● We can create your own client-side components, controls, and behaviors, and use them independently or in conjunction with a custom ASP.NET server control. 17.7 REFERENCE FOR FURTHER READING 1. Beginning ASP.NET 4.5 in C#, Matthew MacDonald, Apress(2012) 2. The Complete Reference ASP .NET, MacDonald, Tata McGraw Hill 3. Beginning ASP.NET 4 in C# and VB Imar Spanajaars, WROX 17.8 UNIT END EXERCISES 1. What is the use of ScriptManager in ASP.NET AJAX? 2. Explain the Partial Refreshes with an example. 3. Explain Progress Notification with the help of an example? 4. Write a short note on Timed Refreshes?  munotes.in