Version: 2019.4
public void RegisterCallback (EventCallback<TEventType> callback, UIElements.TrickleDown useTrickleDown);
public void RegisterCallback (EventCallback<TEventType,TUserArgsType> callback, TUserArgsType userArgs, UIElements.TrickleDown useTrickleDown);


callbackThe event handler to add.
useTrickleDownBy default, this callback is called during the BubbleUp phase. Pass TrickleDown.TrickleDown to call this callback during the TrickleDown phase.
userArgsData to pass to the callback.


Adds an event handler to the instance. If the event handler has already been registered for the same phase (either TrickleDown or BubbleUp) then this method has no effect.