Walkthrough: Creating a Basic ASP.NET AJAX-enabled Web Part

This walkthrough describes the steps for creating a basic ASP.NET AJAX-enabled Web Part that you can add to your Web Part page. The example creates a SayHello Web Part that derives from the ASP.NET 2.0 WebPart Class (in the System.Web.UI.WebControls.WebParts Namespace in the ASP.NET Class Library) for use in a Windows SharePoint Services 3.0 Web site.

Note:
For more information about ASP.NET Web Parts, see ASP.NET Web Parts Overview and Introducing Web Part Controls.

Prerequisites

Windows SharePoint Services 3.0

Visual Studio 2005

Step 1: Create a Web Part Project

To create an AJAX-enabled Web Part control, you start by creating a class library project in the class library in Visual Studio 2005.

To create an ASP.NET Web Part project in Visual Studio 2005

Start Visual Studio 2005.
On the File menu, point to New, and then click Project.
In Project Types, under Visual Basic or C#, select Windows.
In the Templates pane, select Class Library.
Type Sample.SayHello as the project name.

Step 2: Rename the base class and add required namespaces

After you create the project, a blank class file is displayed. You can change the default class name of Class1 to easily identify your new Web Part. In a class library project, only a few namespaces are included. You need to add two required namespaces and references to their assemblies. You must also derive the base class from System.Web.UI.WebControls.WebParts.WebPart. Then, you must add two global variables to update the user interface (UI).

To add namespace references and shared UI components

Rename the default class by selecting Class1.cs in Solution Explorer, right-click, click Rename, and type SayHelloWebPart as the file name.
On the Project menu, click Add Reference.
In the Add Reference dialog on the .NET tab, select System.Web.Extensions and click OK.
Repeat steps 2 and 3 for the System.Web namespace.

In the references area of the class file, add a reference to System.Web.UI.WebControls and create two private variables for the UI, as shown in the following code.

using System;
using System.Text;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
namespace Sample.SayHello
{
   public class SayHelloWebPart : WebPart
   {
     private Label displayName;
     private TextBox inputName;
   }
}

Visual Basic

Imports System
Imports System.Text
Imports System.Web.UI
Imports System.Web.UI.WebControls
Imports System.Web.UI.WebControls.WebParts
Public Class SayHelloWebPart
   Inherits WebPart
   Private displayName As Label
   Private inputName as TextBox
End Class

You have now created a basic structure for the Web Part.

Step 3: Override CreateChildControls and create a button event handler

After configuring the new class to act as a Web Part, you must override the CreateChildControls method to build the UI. You must also add a button handler to refresh the display data.

To override CreateChildControls and create a button event handler

In the SayHelloWebPart.cs file, copy and paste the following code to override the CreateChildControls method

protected override void CreateChildControls()
{
   base.CreateChildControls();

   //Fix for the UpdatePanel postback behaviour.
   EnsurePanelFix();

   LinkButton sayHello = new LinkButton();
   UpdatePanel refreshName = new UpdatePanel();
   ScriptManager scriptHandler = new ScriptManager();
   displayName = new Label();
   inputName = new TextBox();

   //Set up control properties.
   this.displayName.ID = "displayName";
   this.displayName.Text = "Hello!";
   this.inputName.ID = "inputName";
   sayHello.ID = "sayHello";
   sayHello.Text = "Say Hello";
   scriptHandler.ID = "scriptHandler";
   refreshName.ID = "refreshName";
   refreshName.UpdateMode = UpdatePanelUpdateMode.Conditional;
   refreshName.ChildrenAsTriggers = true;

   //Add the EventHandler to the Button.
   sayHello.Click += new EventHandler(ClickHandler);

   //Add the user interface (UI) controls to the UpdatePanel.
   refreshName.ContentTemplateContainer.Controls.Add(this.inputName);
   refreshName.ContentTemplateContainer.Controls.Add(sayHello);
   refreshName.ContentTemplateContainer.Controls.Add(this.displayName);

   //The ScriptManager control must be added first.
   this.Controls.Add(scriptHandler);
   this.Controls.Add(refreshName);
}

Visual Basic

Protected Overrides Sub CreateChildControls()
   MyBase.CreateChildControls()

   'Fix for the UpdatePanel postback behaviour.
   EnsurePanelFix()

   Dim sayHello As New LinkButton
   Dim refreshName As New UpdatePanel
   Dim scriptHandler As New ScriptManager
   displayName = New Label
   inputName = New TextBox

   'Set up control properties.
   Me.displayName.ID = "displayName"
   Me.displayName.Text = "Hello!"
   Me.inputName.ID = "inputName"
   sayHello.ID = "sayHello"
   sayHello.Text = "Say Hello"
   scriptHandler.ID = "scriptHandler"
   refreshName.ID = "refreshName"
   refreshName.UpdateMode = UpdatePanelUpdateMode.Conditional
   refreshName.ChildrenAsTriggers = True

     'Add the EventHandler to the Button.
   AddHandler sayHello.Click, _
     New EventHandler(AddressOf ClickHandler)

   'Add the user interface (UI) controsl to the UpdatePanel

   refreshName.ContentTemplateContainer.Controls.Add(Me.displayName)
   refreshName.ContentTemplateContainer.Controls.Add(Me.inputName)
   refreshName.ContentTemplateContainer.Controls.Add(sayHello)

   'The ScriptManager must be added first.
   Me.Controls.Add(scriptHandler)
   Me.Controls.Add(refreshName)
End Sub

Then, in the SayHelloWebPart.cs file, copy and paste the following code.

private void ClickHandler(object sender, EventArgs args)
{
   this.displayName.Text = "Hello, " 
     + this.inputName.Text.ToString() + ".";
}

Visual Basic

Private Sub ClickHandler(ByVal sender As Object, _
              ByVal args As EventArgs)
   Me.displayName.Text = "Hello, " & Me.inputName.Text & "!"
End Sub

Now you have created the basic UI and button handling event.

For ASP.NET controls that use the JavaScript _doPostBack() function to commit changes, a regular full-page postback event may occur even when the Web Part is inside an UpdatePanel control. Windows SharePoint Services 3.0 and ASP.NET AJAX cache certain form actions, which can cause a conflict between SharePoint and ASP.NET AJAX. To change this behavior, you must add code to scripts that are running in Windows SharePoint Services 3.0.

Step 4: Modify Windows SharePoint Services 3.0 scripts to change doPostBack() behavior

To modify scripts to ensure proper doPostBack() behavior

In the SayHelloWebPart.cs file, copy and paste the following code.

private void EnsurePanelFix()
{
   if (this.Page.Form != null)
   {
     String fixupScript = @"
     _spBodyOnLoadFunctionNames.push(""_initFormActionAjax"");
     function _initFormActionAjax()
     {
       if (_spEscapedFormAction == document.forms[0].action)
       {
         document.forms[0]._initialAction = 
         document.forms[0].action;
       }
     }
     var RestoreToOriginalFormActionCore = 
       RestoreToOriginalFormAction;
     RestoreToOriginalFormAction = function()
     {
       if (_spOriginalFormAction != null)
       {
         RestoreToOriginalFormActionCore();
         document.forms[0]._initialAction = 
         document.forms[0].action;
       }
     }";
   ScriptManager.RegisterStartupScript(this, 
     typeof(SayHelloWebPart), "UpdatePanelFixup", 
     fixupScript, true);
   }
}

Visual Basic

Private Sub EnsurePanelFix()
   If Me.Page.Form IsNot Nothing Then
     Dim fixupScript As New StringBuilder()

     With fixupScript
       .AppendLine("_spBodyOnLoadFunctionNames.push" & _
       "(""_initFormActionAjax"");")
       .AppendLine("function _initFormActionAjax()")
       .AppendLine("{")
       .AppendLine("if (_spEscapedFormAction == " & _
       "document.forms[0].action)")
       .AppendLine("{")
       .AppendLine("document.forms[0]._initialAction = " & _
       document.forms[0].action;")
       .AppendLine("}")
       .AppendLine("}")
       .AppendLine("var RestoreToOriginalFormActionCore = " & _
       RestoreToOriginalFormAction;")
       .AppendLine("RestoreToOriginalFormAction = function()")
       .AppendLine("{")
       .AppendLine("   if (_spOriginalFormAction != null)")
       .AppendLine("   {")
       .AppendLine("       RestoreToOriginalFormActionCore();")
       .AppendLine("       document.forms[0]._initialAction = " & _
       "document.forms[0].action;")
       .AppendLine("   }")
       .AppendLine("}")
     End With
     ScriptManager.RegisterStartupScript(Me, _
       GetType(SayHelloWebPart), "UpdatePanelFixup", _
       fixupScript.ToString(), True)
   End If
End Sub

Now you have modified the scripts to ensure proper postback handling.

After you have added all of your code to your Web Part project, you can build your sample Web Part and deploy it. For more information about deploying a Web Part, see Walkthrough: Creating a Basic Web Part.

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