DateTimePicker.OnDropDown(EventArgs) DateTimePicker.OnDropDown(EventArgs) DateTimePicker.OnDropDown(EventArgs) Method

定義

引發 DropDown 事件。Raises the DropDown event.

protected:
 virtual void OnDropDown(EventArgs ^ eventargs);
protected virtual void OnDropDown (EventArgs eventargs);
abstract member OnDropDown : EventArgs -> unit
override this.OnDropDown : EventArgs -> unit

參數

eventargs
EventArgs EventArgs EventArgs

包含事件資料的 EventArgsAn EventArgs that contains the event data.

備註

顯示DropDown下拉式日曆時, 就會發生此事件。The DropDown event occurs when the drop-down calendar is shown.

引發事件會透過委派叫用此事件處理常式。Raising an event invokes the event handler through a delegate. 如需詳細資訊, 請參閱處理和引發事件For more information, see Handling and Raising Events.

OnDropDown 方法也允許衍生類別處理事件,而不用附加委派。The OnDropDown method also allows derived classes to handle the event without attaching a delegate. 這是在衍生類別中處理事件的慣用技巧。This is the preferred technique for handling the event in a derived class.

給繼承者的注意事項

在衍生OnDropDown(EventArgs)類別中覆寫時, 請務必呼叫基類OnDropDown(EventArgs)的方法, 讓已註冊的委派能接收事件。When overriding OnDropDown(EventArgs) in a derived class, be sure to call the base class' OnDropDown(EventArgs) method so that registered delegates receive the event.

適用於

另請參閱