CommandEventHandler 委托
表示将处理 Command 事件的方法。
**命名空间:**System.Web.UI.WebControls
**程序集:**System.Web（在 system.web.dll 中）
语法
声明
Public Delegate Sub CommandEventHandler ( _
sender As Object, _
e As CommandEventArgs _
)
用法
Dim instance As New CommandEventHandler(AddressOf HandlerMethod)
public delegate void CommandEventHandler (
Object sender,
CommandEventArgs e
)
public delegate void CommandEventHandler (
Object^ sender,
CommandEventArgs^ e
)
/** @delegate */
public delegate void CommandEventHandler (
Object sender,
CommandEventArgs e
)
JScript 支持使用委托，但不支持进行新的声明。
参数
- sender
事件源。
- e
包含事件数据的 CommandEventArgs。
备注
当单击 Button、ImageButton 或 LinkButton 控件时，会引发 Command 事件。
当创建 CommandEventHandler 委托时，将标识处理事件的方法。若要使该事件与事件处理程序相关联，请将该委托的一个实例添加到事件中。除非移除了该委托，否则每当发生该事件时就调用事件处理程序。有关事件处理程序委托的更多信息，请参见 事件和委托。
示例
下面的示例展示如何为 Button 控件的 Command 事件指定和编写处理程序。此示例使用 Button 控件的 OnClick 属性，以声明方式指定事件处理程序。
<%@ Page Language="VB" AutoEventWireup="True" %>
<html>
<head>
<script runat="server">
Sub CommandBtn_Click(sender As Object, e As CommandEventArgs)
Select e.CommandName
Case "Sort"
' Call the method to sort the list.
Sort_List(CType(e.CommandArgument, String))
Case "Submit"
' Display a message for the Submit button being clicked.
Message.Text = "You clicked the Submit button"
' Test whether the command argument is an empty string ("").
If CType(e.CommandArgument , String) = "" Then
' End the message.
Message.Text &= "."
Else
' Display an error message for the command argument.
Message.Text &= ", however the command argument is not recogized."
End If
Case Else
' The command name is not recognized. Display an error message.
Message.Text = "Command name not recogized."
End Select
End Sub
Sub Sort_List(commandArgument As String)
Select commandArgument
Case "Ascending"
' Insert code to sort the list in ascending order here.
Message.Text = "You clicked the Sort Ascending button."
Case "Descending"
' Insert code to sort the list in descending order here.
Message.Text = "You clicked the Sort Descending button."
Case Else
' The command argument is not recognized. Display an error message.
Message.Text = "Command argument not recogized."
End Select
End Sub
</script>
</head>
<body>
<form runat="server">
<h3>Button CommandName Example</h3>
Click on one of the command buttons.
<br><br>
<asp:Button id="Button1"
Text="Sort Ascending"
CommandName="Sort"
CommandArgument="Ascending"
OnCommand="CommandBtn_Click"
runat="server"/>
<asp:Button id="Button2"
Text="Sort Descending"
CommandName="Sort"
CommandArgument="Descending"
OnCommand="CommandBtn_Click"
runat="server"/>
<br><br>
<asp:Button id="Button3"
Text="Submit"
CommandName="Submit"
OnCommand="CommandBtn_Click"
runat="server"/>
<asp:Button id="Button4"
Text="Unknown Command Name"
CommandName="UnknownName"
CommandArgument="UnknownArgument"
OnCommand="CommandBtn_Click"
runat="server"/>
<asp:Button id="Button5"
Text="Submit Unknown Command Argument"
CommandName="Submit"
CommandArgument="UnknownArgument"
OnCommand="CommandBtn_Click"
runat="server"/>
<br><br>
<asp:Label id="Message" runat="server"/>
</form>
</body>
</html>
<%@ Page Language="C#" AutoEventWireup="True" %>
<html>
<head>
<script runat="server">
void CommandBtn_Click(Object sender, CommandEventArgs e)
{
switch(e.CommandName)
{
case "Sort":
// Call the method to sort the list.
Sort_List((String)e.CommandArgument);
break;
case "Submit":
// Display a message for the Submit button being clicked.
Message.Text = "You clicked the Submit button";
// Test whether the command argument is an empty string ("").
if((String)e.CommandArgument == "")
{
// End the message.
Message.Text += ".";
}
else
{
// Display an error message for the command argument.
Message.Text += ", however the command argument is not recogized.";
}
break;
default:
// The command name is not recognized. Display an error message.
Message.Text = "Command name not recogized.";
break;
}
}
void Sort_List(string commandArgument)
{
switch(commandArgument)
{
case "Ascending":
// Insert code to sort the list in ascending order here.
Message.Text = "You clicked the Sort Ascending button.";
break;
case "Descending":
// Insert code to sort the list in descending order here.
Message.Text = "You clicked the Sort Descending button.";
break;
default:
// The command argument is not recognized. Display an error message.
Message.Text = "Command argument not recogized.";
break;
}
}
</script>
</head>
<body>
<form runat="server">
<h3>Button CommandName Example</h3>
Click on one of the command buttons.
<br><br>
<asp:Button id="Button1"
Text="Sort Ascending"
CommandName="Sort"
CommandArgument="Ascending"
OnCommand="CommandBtn_Click"
runat="server"/>
<asp:Button id="Button2"
Text="Sort Descending"
CommandName="Sort"
CommandArgument="Descending"
OnCommand="CommandBtn_Click"
runat="server"/>
<br><br>
<asp:Button id="Button3"
Text="Submit"
CommandName="Submit"
OnCommand="CommandBtn_Click"
runat="server"/>
<asp:Button id="Button4"
Text="Unknown Command Name"
CommandName="UnknownName"
CommandArgument="UnknownArgument"
OnCommand="CommandBtn_Click"
runat="server"/>
<asp:Button id="Button5"
Text="Submit Unknown Command Argument"
CommandName="Submit"
CommandArgument="UnknownArgument"
OnCommand="CommandBtn_Click"
runat="server"/>
<br><br>
<asp:Label id="Message" runat="server"/>
</form>
</body>
</html>
下面的代码示例演示如何指定事件处理程序，然后以编程方式将指定的事件处理程序添加到 Page_Load 方法的事件中。
<%@ Page Language="VB" AutoEventWireup="True" %>
<html>
<head>
<script runat="server">
Sub CommandBtn_Click(sender As Object, e As CommandEventArgs)
Select e.CommandName
Case "Sort"
' Call the method to sort the list.
Sort_List(CType(e.CommandArgument, String))
Case "Submit"
' Display a message for the Submit button being clicked.
Message.Text = "You clicked the <b>Submit</b> button"
' Test whether the Command Argument is an empty string ("").
If CType(e.CommandArgument , String) = "" Then
' End the message.
Message.Text &= "."
Else
' Display an error message for the command argument.
Message.Text &= ", but the command argument is not recogized."
End If
Case Else
' The command name is not recognized. Display an error message.
Message.Text = "Command name not recogized."
End Select
End Sub
Sub Sort_List(commandArgument As String)
Select commandArgument
Case "Ascending"
' Insert code to sort the list in ascending order here.
Message.Text = "You clicked the <b>Sort Ascending</b> button."
Case "Descending"
' Insert code to sort the list in descending order here.
Message.Text = "You clicked the <b>Sort Descending</b> button."
Case Else
' The command argument is not recognized. Display an error message.
Message.Text = "Command argument not recogized."
End Select
End Sub
Sub Page_Load(sender As Object, e As EventArgs)
' Manually register the event-handling method for the Command
' event of the Button controls.
AddHandler Button1.Command, AddressOf CommandBtn_Click
AddHandler Button2.Command, AddressOf CommandBtn_Click
AddHandler Button3.Command, AddressOf CommandBtn_Click
AddHandler Button4.Command, AddressOf CommandBtn_Click
AddHandler Button5.Command, AddressOf CommandBtn_Click
End Sub
</script>
</head>
<body>
<form runat="server">
<h3>Button CommandName Example</h3>
Click one of the command buttons.
<br><br>
<asp:Button id="Button1"
Text="Sort Ascending"
CommandName="Sort"
CommandArgument="Ascending"
runat="server"/>
<asp:Button id="Button2"
Text="Sort Descending"
CommandName="Sort"
CommandArgument="Descending"
runat="server"/>
<br><br>
<asp:Button id="Button3"
Text="Submit"
CommandName="Submit"
runat="server"/>
<asp:Button id="Button4"
Text="Unknown Command Name"
CommandName="UnknownName"
CommandArgument="UnknownArgument"
runat="server"/>
<asp:Button id="Button5"
Text="Submit Unknown Command Argument"
CommandName="Submit"
CommandArgument="UnknownArgument"
runat="server"/>
<br><br>
<asp:Label id="Message" runat="server"/>
</form>
</body>
</html>
<%@ Page Language="C#" AutoEventWireup="True" %>
<html>
<head>
<script runat="server">
void CommandBtn_Click(Object sender, CommandEventArgs e)
{
switch(e.CommandName)
{
case "Sort":
// Call the method to sort the list.
Sort_List((String)e.CommandArgument);
break;
case "Submit":
// Display a message for the Submit button being clicked.
Message.Text = "You clicked the <b>Submit</b> button";
// Test whether the Command Argument is an empty string ("").
if((String)e.CommandArgument == "")
{
// End the message.
Message.Text += ".";
}
else
{
// Display an error message for the command argument.
Message.Text += ", but the command argument is not recogized.";
}
break;
default:
// The command name is not recognized. Display an error message.
Message.Text = "Command name not recogized.";
break;
}
}
void Sort_List(string commandArgument)
{
switch(commandArgument)
{
case "Ascending":
// Insert code to sort the list in ascending order here.
Message.Text = "You clicked the <b>Sort Ascending</b> button.";
break;
case "Descending":
// Insert code to sort the list in descending order here.
Message.Text = "You clicked the <b>Sort Descending</b> button.";
break;
default:
// The command argument is not recognized. Display an error message.
Message.Text = "Command argument not recogized.";
break;
}
}
void Page_Load(Object sender, EventArgs e)
{
// Manually register the event-handling method for the Command
// event of the Button controls.
Button1.Command += new CommandEventHandler(this.CommandBtn_Click);
Button2.Command += new CommandEventHandler(this.CommandBtn_Click);
Button3.Command += new CommandEventHandler(this.CommandBtn_Click);
Button4.Command += new CommandEventHandler(this.CommandBtn_Click);
Button5.Command += new CommandEventHandler(this.CommandBtn_Click);
}
</script>
</head>
<body>
<form runat="server">
<h3>Button CommandName Example</h3>
Click one of the command buttons.
<br><br>
<asp:Button id="Button1"
Text="Sort Ascending"
CommandName="Sort"
CommandArgument="Ascending"
runat="server"/>
<asp:Button id="Button2"
Text="Sort Descending"
CommandName="Sort"
CommandArgument="Descending"
runat="server"/>
<br><br>
<asp:Button id="Button3"
Text="Submit"
CommandName="Submit"
runat="server"/>
<asp:Button id="Button4"
Text="Unknown Command Name"
CommandName="UnknownName"
CommandArgument="UnknownArgument"
runat="server"/>
<asp:Button id="Button5"
Text="Submit Unknown Command Argument"
CommandName="Submit"
CommandArgument="UnknownArgument"
runat="server"/>
<br><br>
<asp:Label id="Message" runat="server"/>
</form>
</body>
</html>
平台
Windows 98、Windows 2000 SP4、Windows Server 2003、Windows XP Media Center Edition、Windows XP Professional x64 Edition、Windows XP SP2、Windows XP Starter Edition
.NET Framework 并不是对每个平台的所有版本都提供支持。有关受支持版本的列表，请参见系统要求。
版本信息
.NET Framework
受以下版本支持：2.0、1.1、1.0
请参见
参考
System.Web.UI.WebControls 命名空间
CommandEventArgs 类
Button.Command 事件
ImageButton.Command
Button 类
LinkButton
ImageButton