Button.Command Event
Occurs when the Button control is clicked.
Assembly: System.Web (in System.Web.dll)
The Command event is raised when the Button control is clicked. This event is commonly used when a command name, such as Sort, is associated with the Button control. This allows you to create multiple Button controls on a Web page and programmatically determine which Button control is clicked.
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The Command event is raised through the control hierarchy in the form of the BubbleEvent. |
For more information about handling events, see NIB: Consuming Events.
The following code example demonstrates how to specify and code an event handler for the Command event to sort a list when the Button control is clicked. This example specifies the event handler declaratively, using the OnClick property of the Button control.
<%@ 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>
The following code example demonstrates how to specify the event handler and programmatically add it to the event in the Page_Load method.
<%@ 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>
Available since 1.1
