private void popup_Opened(object sender, EventArgs e) { PopupView.MoveFocus(new TraversalRequest(FocusNavigationDirection.First)); if (SelectedForeignKey == 0) { SetSelectedForeignKey(); } var iNotify = PopupView.DataContext as INotifyPropertyChanged; if (iNotify != null) { iNotify.PropertyChanged += INotify_PropertyChanged; } }