PopupListBox GetListBox()
 {
     return((PopupListBox)LayoutHelper.FindElement((FrameworkElement)PopupBaseEditHelper.GetPopup(customizationLayouts).PopupContent, IsListBox));
 }
 void OnCustomizationLayoutsPopupContentSelectionChanged(object sender, SelectionChangedEventArgs e)
 {
     PopupBaseEditHelper.GetOkButton(customizationLayouts).IsEnabled = GetListBox().SelectedItems.Count > 0;
 }