CommandManager.AddCanExecuteHandler Method

Reference

Definition

Namespace:: System.Windows.Input

Assembly:: PresentationCore.dll

Important

Some information relates to prerelease product that may be substantially modified before it’s released. Microsoft makes no warranties, express or implied, with respect to the information provided here.

Attaches the specified CanExecuteRoutedEventHandler to the specified element.

public:
 static void AddCanExecuteHandler(System::Windows::UIElement ^ element, System::Windows::Input::CanExecuteRoutedEventHandler ^ handler);

public static void AddCanExecuteHandler (System.Windows.UIElement element, System.Windows.Input.CanExecuteRoutedEventHandler handler);

static member AddCanExecuteHandler : System.Windows.UIElement * System.Windows.Input.CanExecuteRoutedEventHandler -> unit

Public Shared Sub AddCanExecuteHandler (element As UIElement, handler As CanExecuteRoutedEventHandler)

Parameters

element: UIElement

The element to attach handler to.

handler: CanExecuteRoutedEventHandler

The can execute handler.

Exceptions

ArgumentNullException

element or handler is null.

Examples

The following example creates a CanExecuteRoutedEventHandler and an ExecutedRoutedEventHandler and attaches them to a Button which is a command source for the Help command.

First, the Button is created and associated with the Help command.

<Button Command="ApplicationCommands.Help"
        Name="helpButton">Help</Button>

Next, the CanExecuteRoutedEventHandler and the ExecutedRoutedEventHandler are created.

private void HelpCmdExecuted(object sender, ExecutedRoutedEventArgs e)
{
    // OpenHelpFile opens the help file
    OpenHelpFile();
}

Private Sub HelpCmdExecuted(ByVal sender As Object, ByVal e As ExecutedRoutedEventArgs)
    ' OpenHelpFile opens the help file
    OpenHelpFile()
End Sub

private void HelpCmdCanExecute(object sender, CanExecuteRoutedEventArgs e)
{
    // HelpFilesExists() determines if the help file exists
    if (HelpFileExists() == true)
    {
        e.CanExecute = true;
    }
    else
    {
        e.CanExecute = false;
    }
}

Private Sub HelpCmdCanExecute(ByVal sender As Object, ByVal e As CanExecuteRoutedEventArgs)
    ' HelpFilesExists() determines if the help file exists
    If HelpFileExists() = True Then
        e.CanExecute = True
    Else
        e.CanExecute = False
    End If
End Sub

And finally, the handlers are attached to the Button using the AddCanExecuteHandler and AddExecutedHandler.

CommandManager.AddExecutedHandler(helpButton, HelpCmdExecuted);
CommandManager.AddCanExecuteHandler(helpButton, HelpCmdCanExecute);

CommandManager.AddExecutedHandler(helpButton, AddressOf HelpCmdExecuted)
CommandManager.AddCanExecuteHandler(helpButton, AddressOf HelpCmdCanExecute)

Applies to

Dela via