CommandManager.AddPreviewCanExecuteHandler Metod

Definition

Namnområde:

System.Windows.Input

Sammansättning:

PresentationCore.dll

Kopplar det angivna CanExecuteRoutedEventHandler till det angivna elementet.

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

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

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

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

Parametrar

element

UIElement

Elementet som ska kopplas handler till.

handler

CanExecuteRoutedEventHandler

Kan köra hanteraren.

Undantag

ArgumentNullException

element eller handler är null.

Exempel

I följande exempel skapas en CanExecuteRoutedEventHandler och en ExecutedRoutedEventHandler och bifogas dem till en Button som är en kommandokälla för Help kommandot.

Button Först skapas och associeras med Help kommandot.

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

CanExecuteRoutedEventHandler Därefter skapas ochExecutedRoutedEventHandler.

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())
    {
        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

Slutligen kopplas hanterarna till Button med hjälp av AddCanExecuteHandler och AddExecutedHandler.

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

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

Se även

• RoutedCommand
• ICommand