Button.OnCommand(CommandEventArgs) Methode
Definitie
Belangrijk
Bepaalde informatie heeft betrekking op een voorlopige productversie die aanzienlijk kan worden gewijzigd voordat deze wordt uitgebracht. Microsoft biedt geen enkele expliciete of impliciete garanties met betrekking tot de informatie die hier wordt verstrekt.
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)Parameters
De gebeurtenisgegevens.
Voorbeelden
In het volgende codevoorbeeld ziet u hoe u een gebeurtenis-handler voor de Command gebeurtenis opgeeft en codeert om een lijst te sorteren wanneer op het Button besturingselement wordt geklikt. In dit voorbeeld wordt de gebeurtenis-handler declaratief opgegeven met behulp van de OnClick(EventArgs) methode van het Button besturingselement.
<%@ 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>
In het volgende codevoorbeeld ziet u hoe u de gebeurtenis-handler opgeeft en deze programmatisch toevoegt aan de gebeurtenis in de Page_Load methode.
<%@ 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>
Opmerkingen
De Command gebeurtenis wordt gegenereerd wanneer op het Button besturingselement wordt geklikt. Deze gebeurtenis wordt vaak gebruikt wanneer een opdrachtnaam, zoals Sort, is gekoppeld aan het Button besturingselement. Hiermee kunt u meerdere Button besturingselementen op een webpagina maken en programmatisch bepalen op welk Button besturingselement wordt geklikt.
Note
De Command gebeurtenis wordt gegenereerd via de besturingshiërarchie in de vorm van de BubbleEvent.
Als u een gebeurtenis aanroept, wordt de gebeurtenis-handler via een gemachtigde aangeroepen. Zie Afhandeling en het genereren van gebeurtenissen voor meer informatie.
Met OnCommand de methode kunnen afgeleide klassen de gebeurtenis ook verwerken zonder een gemachtigde te koppelen. Dit is de voorkeurstechniek voor het verwerken van de gebeurtenis in een afgeleide klasse.
Notities voor overnemers
Wanneer u OnCommand(CommandEventArgs) overschrijft in een afgeleide klasse, moet u de methode van OnCommand(CommandEventArgs) de basisklasse aanroepen, zodat geregistreerde gemachtigden de gebeurtenis ontvangen.