OnCommand Method

ImageButton.OnCommand Method

Raises the Command event and allows you to handle the Command event directly.

Namespace: System.Web.UI.WebControls
Assembly: System.Web (in system.web.dll)

protected virtual void OnCommand (
	CommandEventArgs e
)
protected void OnCommand (
	CommandEventArgs e
)
protected function OnCommand (
	e : CommandEventArgs
)
Not applicable.

Parameters

e

A CommandEventArgs that contains the event data.

The Command event is raised when the ImageButton control is clicked. The OnCommand event handler is used to make the ImageButton control behave like a Command button. A command name can be associated with the control by using the CommandName property. This allows multiple ImageButton controls to be placed on the Web page. The value in this property can then be programmatically identified in the OnCommand event handler to determine the appropriate action to perform when each ImageButton control is clicked. The CommandArgument property can also be used to pass additional information about the command, such as specifying ascending order.

NoteNote:

The Command event is raised through the control hierarchy in the form of the BubbleEvent.

Raising an event invokes the event handler through a delegate. For more information, see How to: Consume Events in a Web Forms Application.

The OnCommand method also allows derived classes to handle the event without attaching a delegate. This is the preferred technique for handling the event in a derived class.

Notes to Inheritors: When overriding OnCommand in a derived class, be sure to call the base class's OnCommand method so that registered delegates receive the event.

The following example demonstrates how to specify and code a handler for the Command event to determine which ImageButton control is clicked.

NoteNote:

The following code sample uses the single-file code model and may not work correctly if copied directly into a code-behind file. This code sample must be copied into an empty text file that has an .aspx extension. For more information on the Web Forms code model, see ASP.NET Web Page Code Model.

<%@ Page Language="C#" AutoEventWireup="True" %>
<!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>
    <title>ImageButton CommandName Sample</title>
<script language="C#" runat="server">

      void ImageButton_Command(object sender, CommandEventArgs e) 
      {
         if (e.CommandName == "Sort" && e.CommandArgument == "Ascending")
            Label1.Text = "You clicked the Sort Ascending Button";
         else
            Label1.Text = "You clicked the Sort Descending Button";
      }

   </script>

</head>

<body>

   <form id="form1" runat="server">

      <h3>ImageButton CommandName Sample</h3>

      Click an image.<br /><br />

      <asp:ImageButton id="imagebutton1" runat="server"
           AlternateText="Sort Ascending"
           ImageUrl="images/pict.jpg"
           OnCommand="ImageButton_Command"
           CommandName="Sort"
           CommandArgument="Ascending"/>

      <asp:ImageButton id="imagebutton2" runat="server"
           AlternateText="Sort Descending"
           ImageUrl="image/pict2.jpg"
           OnCommand="ImageButton_Command"
           CommandName="Sort"
           CommandArgument="Descending"/>

      <br /><br />
    
      <asp:label id="Label1" runat="server"/>

   </form>

</body>
</html>


Windows 98, Windows Server 2000 SP4, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition

The Microsoft .NET Framework 3.0 is supported on Windows Vista, Microsoft Windows XP SP2, and Windows Server 2003 SP1.

.NET Framework

Supported in: 3.0, 2.0, 1.1, 1.0

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