Button.OnCommand(CommandEventArgs) 方法
定義
重要
部分資訊涉及發行前產品，在發行之前可能會有大幅修改。 Microsoft 對此處提供的資訊，不做任何明確或隱含的瑕疵擔保。
protected:
virtual void OnCommand(System::Web::UI::WebControls::CommandEventArgs ^ e);protected virtual void OnCommand (System.Web.UI.WebControls.CommandEventArgs e);abstract member OnCommand : System.Web.UI.WebControls.CommandEventArgs -> unit
override this.OnCommand : System.Web.UI.WebControls.CommandEventArgs -> unitProtected Overridable Sub OnCommand (e As CommandEventArgs)參數
事件資料。
範例
下列程式代碼範例示範如何在單擊控件時Button，為事件指定和撰寫事件處理程式Command的程式代碼，以排序列表。 這個範例會使用 OnClick 控件的 Button 屬性，以宣告方式指定事件處理程式。
<%@ 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 runat="server">
<title>Button CommandName Example</title>
<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 id="form1" 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="VB" 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 runat="server">
<title>Button CommandName Example</title>
<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 id="form1" 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>
下列程式代碼範例示範如何指定事件處理程式，並以程序設計方式將它新增至 方法中的 Page_Load 事件。
<%@ 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 runat="server">
<title>Button CommandName Example</title>
<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 id="form1" 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="VB" 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 runat="server">
<title>Button CommandName Example</title>
<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 id="form1" 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>
備註
按兩下控件時，Button就會Command引發事件。 當命令名稱之類的 Sort命令名稱與控件相關聯時，通常會使用這個 Button 事件。 這可讓您在網頁上建立多個 Button 控件，並以程式設計方式判斷單擊哪個 Button 控件。
注意
事件 Command 會以的形式透過控件階層引發 BubbleEvent。
引發事件會透過委派叫用此事件處理常式。 如需詳細資訊，請參閱 處理和引發事件。
OnCommand 方法也允許衍生類別處理事件，而不用附加委派。 這是在衍生類別中處理事件的慣用技巧。
給繼承者的注意事項
當在衍生類別中覆寫 OnCommand(CommandEventArgs) 時，請確定呼叫基底類別的 OnCommand(CommandEventArgs) 方法，使已註冊的委派能接收到事件。
