TreeView.OnBeforeExpand(TreeViewCancelEventArgs) Method

Definition

Namespace:

System.Windows.Forms

Assembly:

System.Windows.Forms.dll

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)

Parameters

e

TreeViewCancelEventArgs

A TreeViewCancelEventArgs that contains the event data.

Remarks

Raising an event invokes the event handler through a delegate. For more information, see Handling and Raising Events.

The OnBeforeExpand method also allows derived classes to handle the event without attaching a delegate. This is the preferred technique for handling the event in a derived class.

Notes to Inheritors

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.

See also

• BeforeExpand
• AfterExpand
• OnAfterExpand(TreeViewEventArgs)