Adds an event handler for the "beforeCollapse" event notification. The beforeCollapse event is fired when the user attempts to collapse a node. Collapsing a node hides all child nodes of that node from view. The event can be cancelled by the handler, in which case the node won't collapse.
[Visual Basic] Public Sub AddOnBeforeCollapse( _ ByVal handler As TreeViewCancelEventHandler _ ) [C#] public void AddOnBeforeCollapse( TreeViewCancelEventHandler handler ); [C++] public: void AddOnBeforeCollapse( TreeViewCancelEventHandler* handler ); [JScript] public function AddOnBeforeCollapse( handler : TreeViewCancelEventHandler );
TreeView Class | TreeView Members | System.WinForms Namespace