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Postback Using Client-Side Script Sample

  • Article
  • 10/17/2014

The following sample creates a custom link button that initiates postback through client-side script (JScript, JavaScript). To build the sample, see the instructions in Server Control Samples.

For an example that is similar in this sample but derives from WebControl see Rendering Server Control Samples.

using System;
using System.Web.UI;
using System.Collections;

namespace CustomControls {
      
      public class MyLinkButton: Control, IPostBackEventHandler{
            
            // Defines the Click event.
            //
            public event EventHandler Click;
            
            // Invokes delegates registered with the Click event.
            //
            protected virtual void OnClick(EventArgs e) {
                  
                  if (Click != null) {
                        Click(this, e);
                  }     
            }
            
            
            // Method of IPostBackEventHandler that raises change events.
            //
            public void RaisePostBackEvent(string eventArgument){
                  
                  OnClick(new EventArgs());
            }

            protected override void Render(HtmlTextWriter output) {
                  
                  output.Write("<a  id=\"" + this.UniqueID + "\" href=\"javascript:" + Page.GetPostBackEventReference(this) +"\">");
                  output.Write(" " + this.UniqueID + "</a>");
            }
      }    
}
[Visual Basic]
Option Explicit
Option Strict

Imports System
Imports System.Web.UI
Imports System.Collections

Namespace CustomControls
   Public Class MyLinkButton
      Inherits Control
      Implements IPostBackEventHandler
      
      ' Defines the Click event.
      '
      Public Event Click As EventHandler
      
      ' Invokes delegates registered with the Click event.
      '
      Protected Overridable Sub OnClick(e As EventArgs)
         RaiseEvent Click(Me, e)
      End Sub
      
      ' Method of IPostBackEventHandler that raises change events.
      '
      Public Sub RaisePostBackEvent(eventArgument As String) Implements IPostBackEventHandler.RaisePostBackEvent
         OnClick(New EventArgs())
      End Sub
      
      Protected Overrides Sub Render(output As HtmlTextWriter)
         output.Write(("<a  id=""" & Me.UniqueID & _
               """ href=""javascript:" & _
               Page.GetPostBackEventReference(Me) & """>"))
         output.Write((" " & Me.UniqueID & "</a>"))
      End Sub
   End Class
End Namespace

Using the Control on a Page

The following ASP.NET page uses the custom link button created in the preceding sample.

<%@ Register TagPrefix="Custom" Namespace="CustomControls" Assembly = "CustomControls" %>     
            
<script language="C#" runat=server> 
   private void Button_Click(Object sender, EventArgs e) {
      TextBox.BackColor = System.Drawing.Color.LightGreen;
      TextBox.Text = "The link button caused postback.";
     }                  
</script>

<html>
<body>
   <form runat=server>                    
      Here is the custom link button.<br>
      <Custom:MyLinkButton Id = "Link"  OnClick = "Button_Click" runat=server/> 
     <br><br>
     <asp:TextBox id = "TextBox" Text = "Click the link" Width = "200"  BackColor = "Cyan" runat=server/> 
     <br>                           
   </form>                          
</body>                       
</html>                       
[Visual Basic]
<%@ Register TagPrefix="Custom" Namespace="CustomControls" Assembly = "CustomControls" %>     
            
<script language="VB" runat=server> 
   Private Sub Button_Click(sender As Object, e As EventArgs)
      TextBox.BackColor = System.Drawing.Color.LightGreen
      TextBox.Text = "The link button caused postback."
   End Sub
</script>

<html>
<body>
   <form runat=server>                    
      Here is the custom link button.<br>
      <Custom:MyLinkButton Id = "Link"  OnClick = "Button_Click" runat=server/> 
     <br><br>
     <asp:TextBox id = "TextBox" Text = "Click the link" Width = "200"  BackColor = "Cyan" runat=server/> 
     <br>                           
   </form>                          
</body>                       
</html>

See Also

Generating Client-Side Script for Postback