The Form.OnFormClosing(FormClosingEventArgs) method removes the current form from the Application.OpenForms collection of the associated System.Windows.Forms.Application.

Raising an event invokes the event handler through a delegate. For more information, see Raising an Event.

The Form.OnFormClosed(FormClosedEventArgs) method also allows derived classes to handle the event without attaching a delegate. Overriding this method is the preferred technique for handling the event in a derived class.