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CommandManager.InvalidateRequerySuggested Method

Forces the CommandManager to raise the RequerySuggested event.

Namespace: System.Windows.Input
Assembly: PresentationCore (in presentationcore.dll)

public static void InvalidateRequerySuggested ()
public static void InvalidateRequerySuggested ()
public static function InvalidateRequerySuggested ()
You cannot use methods in XAML.

The CommandManager only pays attention to certain conditions in determining when the command target has changed, such as change in keyboard focus. In situations where the CommandManager does not sufficiently determine a change in conditions that cause a command to not be able to execute, InvalidateRequerySuggested can be called to force the CommandManager to raise the RequerySuggested event.

The following example uses a DispatcherTimer to periodically call InvalidateRequerySuggested to force the CommandManager to raise the RequerySuggested event. For the full sample, see Disable Command Source Via Dispatcher Timer.

//  System.Windows.Threading.DispatcherTimer.Tick handler
//
//  Updates the current seconds display and calls
//  InvalidateRequerySuggested on the CommandManager to force 
//  the Command to raise the CanExecuteChanged event.
private void dispatcherTimer_Tick(object sender, EventArgs e)
{
    // Updating the Label which displays the current second
    lblSeconds.Content = DateTime.Now.Second;

    // Forcing the CommandManager to raise the RequerySuggested event
    CommandManager.InvalidateRequerySuggested();
}

Windows 98, Windows Server 2000 SP4, Windows CE, Windows Millennium Edition, Windows Mobile for Pocket PC, Windows Mobile for Smartphone, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition

The Microsoft .NET Framework 3.0 is supported on Windows Vista, Microsoft Windows XP SP2, and Windows Server 2003 SP1.

.NET Framework

Supported in: 3.0
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