[SL4] Settare pulsante di defualt

public class DefaultButton {     public static DependencyProperty DefaultButtonProperty = DependencyProperty.RegisterAttached("DefaultButton",                                                                 typeof(Button),                                                                 typeof(DefaultButton),                                                                 new PropertyMetadata(null, DefaultButtonChanged));     private static void DefaultButtonChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)     {         var uiElement = d as UIElement;         var button = e.NewValue as Button;         if (uiElement != null && button != null)         {             uiElement.KeyUp += (sender, arg) =>             {                 var peer = new ButtonAutomationPeer(button);                 if (arg.Key == Key.Enter)                 {                     peer.SetFocus();                     uiElement.Dispatcher.BeginInvoke((Action)delegate                     {                         var invokeProv = peer.GetPattern(PatternInterface.Invoke) as IInvokeProvider;                         if (invokeProv != null)                         {                             if (button.IsEnabled)                             {                                 invokeProv.Invoke();                             }                         }                     });                 }             };         }     }     public static Button GetDefaultButton(UIElement obj)     {         return (Button)obj.GetValue(DefaultButtonProperty);     }     public static void SetDefaultButton(DependencyObject obj, Button button)     {         obj.SetValue(DefaultButtonProperty, button);     } }

XAML
<TextBox utility:DefaultButton.DefaultButton="{Binding ElementName=nomeBottone}"/>