public void Do()
 {
     for (int i = items.Length - 1; i >= 0; i--)
     {
         collection.RemoveInternal(i, items[i]);
     }
     collection.modelProperty.XamlDesignItem.NotifyPropertyChanged(collection.modelProperty);
 }
 public void Do()
 {
     collection.RemoveInternal(index, item);
     collection.modelProperty.XamlDesignItem.NotifyPropertyChanged(collection.modelProperty);
 }