PreviewCanExecuteEvent non eseguito
-
10-07-2019 - |
Domanda
Ho un problema con il mio programma WPF. Sto cercando di creare un oggetto che aggiungerà i gestori a tutti i controlli nello stesso ambito.
La seguente riga non funziona. L'evento non è gestito.
element.AddHandler(CommandManager.PreviewCanExecuteEvent, new CanExecuteRoutedEventHandler(scope.CanExecutedHandler), true);
Ho anche un comando associato al pulsante. Quindi l'idea è che voglio eseguire CanExecute del comando: funziona benissimo. Voglio anche un gestore per PreviewCanExecute: non funziona.
Mi dispiace di non poter spiegare meglio.
Vedi il mio codice qui sotto:
XAML:
<Window.Resources>
<my:PermissionScope x:Key="permissionManager"/>
</Window.Resources>
<StackPanel>
<TextBox Height="23" Name="textBox1" Width="120" />
<Button Content="Permission Required" Command="{Binding Path=PermissionRequired}" my:PermissionScope.SharedPermissionScope="{StaticResource permissionManager}"/>
<Button Content="Permission not required" Command="{Binding Path=PermissionRequired}"/>
</StackPanel>
PermissionScope.cs
public class PermissionScope
{
public static readonly DependencyProperty SharedPermissionScopeProperty =
DependencyProperty.RegisterAttached("SharedPermissionScope", typeof(PermissionScope), typeof(PermissionScope),
new FrameworkPropertyMetadata(null, FrameworkPropertyMetadataOptions.Inherits,
new PropertyChangedCallback(OnUseGlobalSharedPermissionScopeChanged)));
public static void SetSharedPermissionScope(DependencyObject depObj, PermissionScope scope)
{
// never place logic in here, because these methods are not called when things are done in XAML
depObj.SetValue(SharedPermissionScopeProperty, scope);
}
public static PermissionScope GetSharedPermissionScope(DependencyObject depObj)
{
// never place logic in here, because these methods are not called when things are done in XAML
return depObj.GetValue(SharedPermissionScopeProperty) as PermissionScope;
}
private static void OnUseGlobalSharedPermissionScopeChanged(DependencyObject depObj, DependencyPropertyChangedEventArgs args)
{
if (depObj is Button)
{
if (args.OldValue != null)
{
RemoveEventHandlers(depObj as UIElement, args.OldValue as PermissionScope);
}
if (args.NewValue != null)
{
AttachEventHandlers(depObj as UIElement, args.NewValue as PermissionScope);
}
}
}
private static void AttachEventHandlers(UIElement element, PermissionScope scope)
{
if (element != null && scope != null)
{
element.AddHandler(CommandManager.PreviewCanExecuteEvent, new CanExecuteRoutedEventHandler(scope.CanExecutedHandler), true); // we need to see all events to subvert the built-in undo/redo tracking in the text boxes
}
}
private static void RemoveEventHandlers(UIElement element, PermissionScope scope)
{
if (element != null && scope != null)
{
element.AddHandler(CommandManager.PreviewCanExecuteEvent, new CanExecuteRoutedEventHandler(scope.CanExecutedHandler));
}
}
private void CanExecutedHandler(object sender, CanExecuteRoutedEventArgs e)
{
if (e.Command is CommandBase)
{
bool hasPermission = false;
hasPermission = ((CommandBase)e.Command).HasPermission();
ShowControl((UIElement)e.OriginalSource, hasPermission);
}
}
public static void ShowControl(UIElement element, bool show)
{
element.Visibility = show ? Visibility.Visible : Visibility.Collapsed;
}
}
Non ho davvero alcun aiuto.
Cordiali saluti, Michael
Soluzione
Ho scoperto me stesso. Funzionerà solo con RoutedCommands e non con ICommand
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