Chapter 25
How to use AJAX
Murach’s ASP.NET 3.5/C#, C25
© 2008, Mike Murach & Associates, Inc.
Slide 1
Objectives
Applied
 Use the ASP.NET AJAX server controls to develop simple
ASP.NET AJAX applications.
Knowledge
 Distinguish between a normal HTTP request and an AJAX HTTP
request.
 In general terms, describe the Microsoft AJAX Library and the
ASP.NET AJAX controls.
 Describe the use of these ASP.NET AJAX controls:
ScriptManager, UpdatePanel, UpdateProgress, and Timer.
Murach’s ASP.NET 3.5/C#, C25
© 2008, Mike Murach & Associates, Inc.
Slide 2
Standard request and response cycle
Client
HTTP request:
The browser requests a
page.
Server
Browser
Web server
HTTP response:
The server returns the
requested page and the
page is loaded.
Browser
Murach’s ASP.NET 3.5/C#, C25
Web server
© 2008, Mike Murach & Associates, Inc.
Slide 3
AJAX-enabled request and response cycle
AJAX HTTP request:
The browser requests
updated information for a
page.
Client
Server
Browser
Web server
AJAX HTTP response:
The server returns the
requested information and
the page is updated.
Browser
Murach’s ASP.NET 3.5/C#, C25
Web server
© 2008, Mike Murach & Associates, Inc.
Slide 4
AJAX concepts
 A rich Internet application (RIA) is an application that is displayed
in a web browser, but has some of the features of a desktop
application such as an enhanced user interface and quick response
time.
 Asynchronous JavaScript and XML (AJAX) is one way to build a
RIA.
 Each time a standard HTTP request and response cycle is
performed, the entire page is returned from the server and the page
is loaded into the browser.
 With an AJAX HTTP request and response cycle, the browser can
request just the information it needs to update the page. Then, the
updated information that’s returned from the server can be used to
update the page without having to reload it.
Murach’s ASP.NET 3.5/C#, C25
© 2008, Mike Murach & Associates, Inc.
Slide 5
The architecture of AJAX
Web browser
Web page
DOM
Events
5
Web server
1
JavaScript
and
XMLHttpRequest
Murach’s ASP.NET 3.5/C#, C25
2
4
Application server
3
© 2008, Mike Murach & Associates, Inc.
Slide 6
How AJAX works
 The web page that is downloaded from the web server contains
HTML, CSS, and JavaScript.
 The web browser uses the HTML and CSS to build the Document
Object Model (DOM), which is an object-oriented representation of
the content in the page.
 JavaScript is used to run code when events occur in the web page.
JavaScript also has access to the DOM to determine the state of
controls on the page and to make changes to the DOM that will be
shown to the user.
 The XMLHttpRequest object that’s built into the web browser is
used to communicate with the web server. JavaScript is used to
access the functionality of the XMLHttpRequest object.
 For most requests, JavaScript Object Notation (JSON) is now used
to send data back to the web browser
Murach’s ASP.NET 3.5/C#, C25
© 2008, Mike Murach & Associates, Inc.
Slide 7
How AJAX updates the contents of a web page
1. An event happens on the web page. This can be the user moving the
mouse, clicking a button, or changing a field or a timer going off.
This event triggers JavaScript code to execute.
2. JavaScript prepares a request and sends it to the web server. The
request contains information about the event and the current state of
the controls on the web page.
3. The server receives the data and processes it. Although processing
can take place on the client, some actions, such as database access,
must happen on the server.
4. The server prepares a response and sends it back to the browser. The
response contains the updated state of the controls on the web page.
5. JavaScript parses the response and uses the data it contains to update
the contents of the web page by modifying objects in the DOM. The
browser then updates the user’s screen.
Murach’s ASP.NET 3.5/C#, C25
© 2008, Mike Murach & Associates, Inc.
Slide 8
The architecture of ASP.NET AJAX
Web browser
Web page
DOM
Events
Web server
ASP.NET application server
JavaScript
Microsoft AJAX Library
Murach’s ASP.NET 3.5/C#, C25
ASP.NET AJAX server controls
ASP.NET AJAX Control Toolkit
© 2008, Mike Murach & Associates, Inc.
Slide 9
Components of ASP.NET AJAX
 Microsoft AJAX Library
 ASP.NET AJAX server controls
 ASP.NET AJAX Control Toolkit
Murach’s ASP.NET 3.5/C#, C25
© 2008, Mike Murach & Associates, Inc.
Slide 10
How ASP.NET AJAX works
 Microsoft developed a set of extensions to ASP.NET 2.0 that
provided AJAX support. These extensions were incorporated as
built-in features of ASP.NET 3.5 and Visual Studio 2008.
 ASP.NET uses an asynchronous postback to perform a partialpage update. During an asynchronous postback, the view state of
the web page is sent to the server, which processes the request and
sends back the new view state of the controls being updated.
 The ASP.NET AJAX server controls enclose other ASP.NET
server controls to make them AJAX-enabled. These controls can
then be updated using an asynchronous postback.
 A single page can have one or more groups of AJAX-enabled
controls that can be updated independently or simultaneously.
 Server controls that are not AJAX-enabled will still trigger a full
postback that causes the entire page to be reloaded.
Murach’s ASP.NET 3.5/C#, C25
© 2008, Mike Murach & Associates, Inc.
Slide 11
Features of the Microsoft AJAX Library
 Cross-browser compatibility
 Debugging
 JavaScript type extensions
 Globalization and localization
 Event handling
 Networking
 Classes and namespaces
 JSON serialization
 Inheritance and interfaces
 Components
 Reflection
 Partial-page updates
 Exception handling
 Application services
Murach’s ASP.NET 3.5/C#, C25
© 2008, Mike Murach & Associates, Inc.
Slide 12
ASP.NET AJAX server controls
 ScriptManager
 ScriptManagerProxy
 UpdatePanel
 UpdateProgress
 Timer
Murach’s ASP.NET 3.5/C#, C25
© 2008, Mike Murach & Associates, Inc.
Slide 13
The ScriptManager control
 You can only have one ScriptManager control on a page. This
includes master and content pages.
 If there is more than one ScriptManager control on a page, an
Invalid Operation exception will be generated.
 The ScriptManager control can also be used to load and manage
additional JavaScript files and to register web services so they can
be accessed by JavaScript code on the client through a web service
proxy.
Murach’s ASP.NET 3.5/C#, C25
© 2008, Mike Murach & Associates, Inc.
Slide 14
The ScriptManagerProxy control
 The ScriptManagerProxy control lets you load JavaScript files and
register web services.
 This control can be used:
 in a content page if the master page contains a ScriptManager
control
 in a user control that will be used on pages that contain a
ScriptManager control
Murach’s ASP.NET 3.5/C#, C25
© 2008, Mike Murach & Associates, Inc.
Slide 15
The UpdatePanel control
 The UpdatePanel control is a container control that holds other
server controls that will be updated during an asynchronous
postback.
 All controls inside an UpdatePanel control will be updated at the
same time.
 A page can contain multiple UpdatePanel controls, each with a
different set of controls.
Murach’s ASP.NET 3.5/C#, C25
© 2008, Mike Murach & Associates, Inc.
Slide 16
The UpdateProgress control
 You can use the UpdateProgress control to visually indicate that an
asynchronous postback is in progress and that the user should wait
until it’s completed before doing anything else on the page.
 This is useful when an asynchronous postback will take a few
seconds or more to complete.
The Timer control
 When one or more UpdatePanel controls need to be updated
automatically, you can use the Timer control to trigger partial-page
updates at a set time interval.
Murach’s ASP.NET 3.5/C#, C25
© 2008, Mike Murach & Associates, Inc.
Slide 17
Common ASP.NET AJAX Control Toolkit controls
 Accordion
 PagingBulletedList
 Animation
 PopupControl
 Calendar
 RoundedCorners
 CollapsiblePanel
 Slider
 DragPanel
 SlideShow
 DropShadow
 TabContainer
 HoverMenu
 TextBoxWatermark
 ModalPopup
 ToggleButton
 NumericUpDown
Murach’s ASP.NET 3.5/C#, C25
© 2008, Mike Murach & Associates, Inc.
Slide 18
Web sites related to the
ASP.NET AJAX Control Toolkit
 www.asp.net/ajax/ajaxcontroltoolkit/samples/
 www.codeplex.com/AtlasControlToolkit/Release/ProjectReleases.aspx
Murach’s ASP.NET 3.5/C#, C25
© 2008, Mike Murach & Associates, Inc.
Slide 19
Common attributes of the ScriptManager control
 AsyncPostBackTimeout
 EnablePageMethods
 EnableScriptGlobalization
 EnableScriptLocalization
 IsInAsyncPostBack
 LoadScriptsBeforeUI
The aspx code for a ScriptManager control
<asp:ScriptManager ID="ScriptManager1" runat="server">
</asp:ScriptManager>
Murach’s ASP.NET 3.5/C#, C25
© 2008, Mike Murach & Associates, Inc.
Slide 20
The aspx code for a ScriptManager control that
registers scripts
<asp:ScriptManager ID="ScriptManager1" runat="server">
<Scripts>
<asp:ScriptReference
Path="~/Scripts/SampleScript.js" />
<asp:ScriptReference Assembly="SampleAssembly"
Name="SampleAssembly.SampleScript.js" />
</Scripts>
</asp:ScriptManager>
The aspx code for a ScriptManager control that
registers a web service
<asp:ScriptManager ID="ScriptManager1" runat="server">
<Services>
<asp:ServiceReference
Path="~/Services/SampleService.asmx" />
</Services>
</asp:ScriptManager>
Murach’s ASP.NET 3.5/C#, C25
© 2008, Mike Murach & Associates, Inc.
Slide 21
A content page with a ScriptManagerProxy control
Murach’s ASP.NET 3.5/C#, C25
© 2008, Mike Murach & Associates, Inc.
Slide 22
The aspx code for the ScriptManagerProxy control
<asp:ScriptManagerProxy ID="ScriptManagerProxy1"
runat="server">
</asp:ScriptManagerProxy>
The aspx code for a ScriptManagerProxy control
that registers scripts
<asp:ScriptManagerProxy ID="ScriptManager1"
runat="server">
<Scripts>
<asp:ScriptReference
Path="~/Scripts/SampleScript.js" />
<asp:ScriptReference Assembly="SampleAssembly"
Name="SampleAssembly.SampleScript.js" />
</Scripts>
</asp:ScriptManagerProxy>
Murach’s ASP.NET 3.5/C#, C25
© 2008, Mike Murach & Associates, Inc.
Slide 23
The aspx code for a ScriptManagerProxy control
that registers a web service
<asp:ScriptManagerProxy ID="ScriptManager1"
runat="server">
<Services>
<asp:ServiceReference
Path="~/Services/SampleService.asmx" />
</Services>
</asp:ScriptManagerProxy>
Murach’s ASP.NET 3.5/C#, C25
© 2008, Mike Murach & Associates, Inc.
Slide 24
Two attributes of the UpdatePanel control
Attribute
Description
ChildrenAsTriggers Determines if the controls in a panel are
treated as triggers that cause the content of the
panel to be updated when a control causes a
postback. The default is True.
UpdateMode
Determines when the content of a panel is
updated (Always or Conditional). A nested
UpdatePanel control will always be updated
when its parent UpdatePanel control is
updated. The default is Always.
Murach’s ASP.NET 3.5/C#, C25
© 2008, Mike Murach & Associates, Inc.
Slide 25
The starting aspx code for an UpdatePanel control
<asp:UpdatePanel ID="UpdatePanel1" runat="server">
<ContentTemplate>
</ContentTemplate>
</asp:UpdatePanel>
The aspx code for an UpdatePanel control that
specifies triggers
<asp:UpdatePanel ID="UpdatePanel1" runat="server">
<ContentTemplate>
<asp:Button ID="Button2" runat="server"
Text="Add" />
</ContentTemplate>
<Triggers>
<asp:AsyncPostBackTrigger ControlID="Button1"
EventName="Click" />
<asp:PostBackTrigger ControlID="Button2" />
</Triggers>
</asp:UpdatePanel>
Murach’s ASP.NET 3.5/C#, C25
© 2008, Mike Murach & Associates, Inc.
Slide 26
Controls that have compatibility issues with the
UpdatePanel control
 GridView
 DetailsView
 TreeView
 Menu
 FileUpload
 Login
 PasswordRecovery
 ChangePassword
 CreateUserWizard
Murach’s ASP.NET 3.5/C#, C25
© 2008, Mike Murach & Associates, Inc.
Slide 27
A Timer control in Design view
Murach’s ASP.NET 3.5/C#, C25
© 2008, Mike Murach & Associates, Inc.
Slide 28
Two attributes of the Timer control
Attribute
Interval
Enabled
Murach’s ASP.NET 3.5/C#, C25
Description
Determines how often in milliseconds the
control will trigger an asynchronous postback.
The default value is 60,000 milliseconds (60
seconds).
Determines whether a postback occurs when the
time specified by the Interval attribute elapses.
The default is True.
© 2008, Mike Murach & Associates, Inc.
Slide 29
The aspx code for an UpdatePanel control with a
Timer control
<asp:UpdatePanel ID="UpdatePanel1" runat="server">
<ContentTemplate>
<asp:Timer ID="Timer1" runat="server"
Interval="10000">
</asp:Timer>
</ContentTemplate>
</asp:UpdatePanel>
Murach’s ASP.NET 3.5/C#, C25
© 2008, Mike Murach & Associates, Inc.
Slide 30
An UpdateProgress control in Design view
Murach’s ASP.NET 3.5/C#, C25
© 2008, Mike Murach & Associates, Inc.
Slide 31
Three attributes of the UpdateProgress control
Attribute
DynamicLayout
Description
Determines whether space is allocated
on the page for the content of the control
when it isn’t displayed. The default is
True.
DisplayAfter
Determines how long in milliseconds
after the asynchronous postback has
started to display the content. The
default is 500 milliseconds (0.5
seconds).
AssociatedUpdatePanelID The ID of the UpdatePanel control that
the control is associated with.
Murach’s ASP.NET 3.5/C#, C25
© 2008, Mike Murach & Associates, Inc.
Slide 32
The aspx code for an UpdatePanel control with an
UpdateProgress control
<asp:UpdatePanel ID="UpdatePanel1" runat="server">
<ContentTemplate>
<asp:UpdateProgress ID="UpdateProgress1"
runat="server">
<ProgressTemplate>
Please wait. The update is in progress.
</ProgressTemplate>
</asp:UpdateProgress>
</ContentTemplate>
</asp:UpdatePanel>
Murach’s ASP.NET 3.5/C#, C25
© 2008, Mike Murach & Associates, Inc.
Slide 33
The Shout Box application
Murach’s ASP.NET 3.5/C#, C25
© 2008, Mike Murach & Associates, Inc.
Slide 34
The ShoutItem.cs file
using System;
public class ShoutItem
{
public string UserName;
public DateTime Timestamp;
public string Comment;
}
Murach’s ASP.NET 3.5/C#, C25
© 2008, Mike Murach & Associates, Inc.
Slide 35
The ShoutItemList.cs file
using System;
using System.Collections.Generic;
using System.Text;
public class ShoutItemList
{
private List<ShoutItem> shoutList =
new List<ShoutItem>();
private void Purge(){
DateTime purgeTime = DateTime.Now;
purgeTime = purgeTime.AddMinutes(-3);
int i = 0;
while (i < shoutList.Count){
if (shoutList[i].Timestamp <= purgeTime)
shoutList.RemoveAt(i);
else
i += 1;
}
}
Murach’s ASP.NET 3.5/C#, C25
© 2008, Mike Murach & Associates, Inc.
Slide 36
The ShoutItemList.cs file (cont.)
public void Add(ShoutItem shout){
Purge();
System.Threading.Thread.Sleep(2000);
shoutList.Insert(0, shout);
}
public string Display(){
Purge();
StringBuilder shoutBoxText = new StringBuilder();
if (shoutList.Count > 0){
shoutBoxText.AppendLine("<dl>");
foreach (ShoutItem shout in shoutList){
shoutBoxText.Append(
"<dt>" + shout.UserName);
shoutBoxText.Append(" (");
shoutBoxText.Append(
shout.Timestamp.ToShortDateString());
shoutBoxText.AppendLine(")</dt>");
shoutBoxText.AppendLine("<dd>"
+ shout.Comment + "</dd>");
}
Murach’s ASP.NET 3.5/C#, C25
© 2008, Mike Murach & Associates, Inc.
Slide 37
The ShoutItemList.cs file (cont.)
shoutBoxText.AppendLine("</dl>");
}
return shoutBoxText.ToString();
}
}
Murach’s ASP.NET 3.5/C#, C25
© 2008, Mike Murach & Associates, Inc.
Slide 38
The Default.aspx file: Shout Box application
<%@ Page Language="C#" AutoEventWireup="true"
CodeFile="Default.aspx.cs" Inherits="_Default" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0
Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
<title>Chapter 25: Product List with AJAX Shout Box
</title>
<style type="text/css">
.style1 {width: 100px;}
.style2 {width: 200px;}
.style3 {width: 80px;}
.style4 {width: 390px;}
.style5 {width: 10px;}
.style6 {width: 290px;}
.style7 {width: 75px;}
.style8 {width: 225px;}
</style>
Murach’s ASP.NET 3.5/C#, C25
© 2008, Mike Murach & Associates, Inc.
Slide 39
The Default.aspx file (cont.)
<link href="ShoutBox.css" rel="stylesheet"
type="text/css" />
</head>
<body>
<form id="form1" runat="server">
<div>
<asp:Image ID="Image1" runat="server"
ImageUrl="~/Images/banner.jpg" />
<br /><br />
Choose a category:&nbsp;
<asp:DropDownList ID="Category" runat="server"
AutoPostBack="True"
Width="130px" DataSourceID="SqlDataSource1"
DataTextField="LongName"
DataValueField="CategoryID">
</asp:DropDownList>
Murach’s ASP.NET 3.5/C#, C25
© 2008, Mike Murach & Associates, Inc.
Slide 40
The Default.aspx file (cont.)
<asp:SqlDataSource ID="SqlDataSource1" runat="server"
ConnectionString=
"<%$ ConnectionStrings:HalloweenConnectionString %>"
SelectCommand="SELECT [CategoryID], [LongName]
FROM [Categories]
ORDER BY [LongName]">
</asp:SqlDataSource>
<br /><br />
<table>
<tr>
<td class="style4" valign="top">
<asp:DataList ID="DataList1" runat="server"
DataSourceID="SqlDataSource2"
BackColor="White" BorderColor="#999999"
BorderStyle="Solid" BorderWidth="1px"
CellPadding="3" ForeColor="Black"
GridLines="Vertical">
Murach’s ASP.NET 3.5/C#, C25
© 2008, Mike Murach & Associates, Inc.
Slide 41
The Default.aspx file (cont.)
<HeaderTemplate>
<table>
<tr>
<td class="style1">ID</td>
<td class="style2">Product</td>
<td class="style3" align="right">
Unit Price</td>
<td class="style3" align="right">
On Hand</td>
</tr>
</table>
</HeaderTemplate>
Murach’s ASP.NET 3.5/C#, C25
© 2008, Mike Murach & Associates, Inc.
Slide 42
The Default.aspx file (cont.)
<ItemTemplate>
<table><tr>
<td class="style1">
<asp:Label ID="ProductID" runat="server"
Text='<%# Eval("ProductID") %>'>
</asp:Label></td>
<td class="style2">
<asp:Label ID="ProductName"
runat="server"
Text='<%# Eval("Name") %>'>
</asp:Label></td>
<td class="style3" align="right">
<asp:Label ID="UnitPrice" runat="server"
Text=
'<%# Eval("UnitPrice", "{0:c}") %>'>
</asp:Label></td>
<td class="style3" align="right">
<asp:Label ID="OnHand" runat="server"
Text='<%# Eval("OnHand") %>'>
</asp:Label></td>
</tr></table>
Murach’s ASP.NET 3.5/C#, C25
© 2008, Mike Murach & Associates, Inc.
Slide 43
The Default.aspx file (cont.)
</ItemTemplate>
<AlternatingItemStyle BackColor="#CCCCCC" />
<HeaderStyle BackColor="Black" Font-Bold="True"
ForeColor="White" />
</asp:DataList></td>
<td class="style5"></td>
<td class="style6" valign="top">
<asp:ScriptManager ID="ScriptManager1"
runat="server">
</asp:ScriptManager>
Here's what everyone is saying:<br /><br />
<asp:UpdatePanel ID="ShoutBoxPanel1"
runat="server">
<ContentTemplate>
<asp:Label ID="lblShoutBox"
runat="server"></asp:Label>
<asp:Timer ID="Timer1" runat="server"
Interval="5000">
</asp:Timer>
</ContentTemplate>
Murach’s ASP.NET 3.5/C#, C25
© 2008, Mike Murach & Associates, Inc.
Slide 44
The Default.aspx file (cont.)
<Triggers>
<asp:AsyncPostBackTrigger
ControlID="btnAddShout"
EventName="Click" />
</Triggers>
</asp:UpdatePanel><br />
<asp:UpdatePanel ID="ShoutBoxPanel2"
runat="server" UpdateMode="Conditional">
<ContentTemplate>
<table>
<tr>
<td class="style7">Name:</td>
<td class="style8">
<asp:TextBox ID="txtUserName"
runat="server" MaxLength="15"
Width="100px"></asp:TextBox></td>
</tr>
Murach’s ASP.NET 3.5/C#, C25
© 2008, Mike Murach & Associates, Inc.
Slide 45
The Default.aspx file (cont.)
<tr>
<td class="style7">Shout:</td>
<td class="style8">
<asp:TextBox ID="txtShout"
runat="server" MaxLength="255"
Width="220px"></asp:TextBox></td>
</tr>
</table>
<asp:RequiredFieldValidator
ID="RequiredFieldValidator1"
runat="server"
ErrorMessage="Name is required."
ControlToValidate="txtUserName"
Display="Dynamic">
</asp:RequiredFieldValidator>
Murach’s ASP.NET 3.5/C#, C25
© 2008, Mike Murach & Associates, Inc.
Slide 46
The Default.aspx file (cont.)
<asp:RequiredFieldValidator
ID="RequiredFieldValidator2"
runat="server"
ErrorMessage="Shout is required."
ControlToValidate="txtShout"
Display="Dynamic">
</asp:RequiredFieldValidator>
<asp:Button ID="btnAddShout" runat="server"
Text="Add Shout" />
<asp:UpdateProgress ID="UpdateProgress1"
runat="server" DynamicLayout="False">
<ProgressTemplate>
<img src="Images/spinner.gif"
alt="Please Wait"
style="vertical-align: middle" />
Uploading Comment...
</ProgressTemplate>
</asp:UpdateProgress>
</ContentTemplate>
</asp:UpdatePanel>
</td>
Murach’s ASP.NET 3.5/C#, C25
© 2008, Mike Murach & Associates, Inc.
Slide 47
The Default.aspx file (cont.)
</tr>
</table>
<asp:SqlDataSource ID="SqlDataSource2" runat="server"
ConnectionString=
"<%$ ConnectionStrings:HalloweenConnectionString %>"
SelectCommand="SELECT [ProductID], [Name],
[UnitPrice], [OnHand]
FROM [Products]
WHERE ([CategoryID] = @CategoryID)
ORDER BY [ProductID]">
<SelectParameters>
<asp:ControlParameter Name="CategoryID"
Type="String" ControlID="Category"
PropertyName="SelectedValue" />
</SelectParameters>
</asp:SqlDataSource>
</div>
</form>
</body>
</html>
Murach’s ASP.NET 3.5/C#, C25
© 2008, Mike Murach & Associates, Inc.
Slide 48
The ShoutBox.css file
#ShoutBoxPanel1
{
height: 300px;
border: solid 1px black;
overflow: auto;
}
#ShoutBoxPanel1 dl
{
margin-top: 0px;
}
Murach’s ASP.NET 3.5/C#, C25
© 2008, Mike Murach & Associates, Inc.
Slide 49
The Default.aspx.cs file: Shout Box application
using
using
using
using
using
using
using
using
using
using
using
System;
System.Configuration;
System.Data;
System.Linq;
System.Web;
System.Web.Security;
System.Web.UI;
System.Web.UI.HtmlControls;
System.Web.UI.WebControls;
System.Web.UI.WebControls.WebParts;
System.Xml.Linq;
Murach’s ASP.NET 3.5/C#, C25
© 2008, Mike Murach & Associates, Inc.
Slide 50
The Default.aspx.cs file (cont.)
public partial class _Default : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{
ShoutItemList shoutBox;
if (Application["ShoutBox"] == null)
{
shoutBox = new ShoutItemList();
Application.Add("ShoutBox", shoutBox);
}
else
{
shoutBox = (ShoutItemList)
Application["ShoutBox"];
lblShoutBox.Text = shoutBox.Display();
}
if (ScriptManager1.IsInAsyncPostBack != true)
txtUserName.Focus();
}
Murach’s ASP.NET 3.5/C#, C25
© 2008, Mike Murach & Associates, Inc.
Slide 51
The Default.aspx.cs file (cont.)
protected void btnAddShout_Click(object sender,
EventArgs e)
{
ShoutItem shout = new ShoutItem();
shout.UserName = txtUserName.Text;
shout.Comment = txtShout.Text;
shout.Timestamp = DateTime.Now;
Application.Lock();
ShoutItemList shoutBox = (ShoutItemList)
Application["ShoutBox"];
shoutBox.Add(shout);
Application.UnLock();
lblShoutBox.Text = shoutBox.Display();
txtShout.Text = "";
txtShout.Focus();
}
}
Murach’s ASP.NET 3.5/C#, C25
© 2008, Mike Murach & Associates, Inc.
Slide 52