TreeView.OnBeforeExpand(TreeViewCancelEventArgs) 方法

定义

引发 BeforeExpand 事件。Raises the BeforeExpand event.

protected:
 virtual void OnBeforeExpand(System::Windows::Forms::TreeViewCancelEventArgs ^ e);
protected virtual void OnBeforeExpand (System.Windows.Forms.TreeViewCancelEventArgs e);
abstract member OnBeforeExpand : System.Windows.Forms.TreeViewCancelEventArgs -> unit
override this.OnBeforeExpand : System.Windows.Forms.TreeViewCancelEventArgs -> unit
Protected Overridable Sub OnBeforeExpand (e As TreeViewCancelEventArgs)

参数

e
TreeViewCancelEventArgs

包含事件数据的 TreeViewCancelEventArgsA TreeViewCancelEventArgs that contains the event data.

注解

引发事件时,将通过委托调用事件处理程序。Raising an event invokes the event handler through a delegate. 有关详细信息,请参阅 处理和引发事件For more information, see Handling and Raising Events.

OnBeforeExpand 方法还允许派生类对事件进行处理而不必附加委托。The OnBeforeExpand method also allows derived classes to handle the event without attaching a delegate. 这是在派生类中处理事件的首选技术。This is the preferred technique for handling the event in a derived class.

继承者说明

在派生类中重写 OnBeforeExpand(TreeViewCancelEventArgs) 时,一定要调用基类的 OnBeforeExpand(TreeViewCancelEventArgs) 方法,以便已注册的委托对事件进行接收。When overriding OnBeforeExpand(TreeViewCancelEventArgs) in a derived class, be sure to call the base class's OnBeforeExpand(TreeViewCancelEventArgs) method so that registered delegates receive the event.

适用于

另请参阅