Adds an event handler for the "beforeExpand" event notification. The beforeExpand event is fired when the user attempts to expand a node. Expanding a node causes its child nodes to be displayed. The event can be cancelled by the handler, in which case the node won't expand.
[Visual Basic] Public Sub AddOnBeforeExpand( _ ByVal handler As TreeViewCancelEventHandler _ ) [C#] public void AddOnBeforeExpand( TreeViewCancelEventHandler handler ); [C++] public: void AddOnBeforeExpand( TreeViewCancelEventHandler* handler ); [JScript] public function AddOnBeforeExpand( handler : TreeViewCancelEventHandler );
TreeView Class | TreeView Members | System.WinForms Namespace