CommandManager.AddCanExecuteHandler 方法

定义

命名空间:
System.Windows.Input
程序集:
PresentationCore.dll

将指定的 CanExecuteRoutedEventHandler 元素附加到指定的元素。

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)

参数

element
UIElement

要附加到 handler 的元素。

handler
CanExecuteRoutedEventHandler

可以执行处理程序。

例外

ArgumentNullException

element 或 handler 为 null.

示例

以下示例创建一个和一个CanExecuteRoutedEventHandlerExecutedRoutedEventHandler命令，并将其Button附加到该命令的命令源Help。

首先， Button 创建该命令并将其关联 Help 。

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

接下来，创建 CanExecuteRoutedEventHandler 和 ExecutedRoutedEventHandler 创建。

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

最后，处理程序附加到 Button using AddCanExecuteHandler and AddExecutedHandler.

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

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

适用于

另请参阅