private static extern void DragDrop_DoDragDrop(HandleRef source, HandleRef data, int allowedEffects, int callbackId, Callback_DragDropCompleted callback);
private static void DoDragDropHelper(DependencyObject source, object data, DragDropEffects allowedEffects, int callbackId, Callback_DragDropCompleted callback) { DragDrop_DoDragDrop(DependencyObject.getCPtr(source), Extend.GetInstanceHandle(data), (int)allowedEffects, callbackId, callback); }