CommandManager.AddCanExecuteHandler Method

Definition

Namespace:

System.Windows.Input

Assembly:

PresentationCore.dll

Attaches the specified CanExecuteRoutedEventHandler to the specified element.

C#

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

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.

XAML

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

Next, the CanExecuteRoutedEventHandler and the ExecutedRoutedEventHandler are created.

C#

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

C#

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

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

C#

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

Applies to

See also

• RoutedCommand
• ICommand