Raising an event invokes the event handler through a delegate. The OnCrosshairWidthChanged 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 OnCrosshairWidthChanged in a derived class, be sure to call the base class's OnCrosshairWidthChanged method so that registered delegates receive the event.