Sometimes, the event passed to method is not the wanted event, eg. clicking on menu item giving the event of menu item. In order to get the event of the UI element which triggers the menu, get that original UI event with:
// Working with method:, menu:, dialog:
// For menu case, the callback of menu item gets the same event.
ui.get_ui_event();
ui.set_ondragstart(Ele,Data);
ui.set_ondrop(Ele,handler_method);