Raises the Control.MouseWheel event
The System.Windows.Forms.ScrollBar control will convert mouse wheel movements to scrolling when the System.Windows.Forms.ScrollBar is in focus.
Raising an event invokes the event handler through a delegate. For more information, see Raising an Event.
The ScrollBar.OnMouseWheel(MouseEventArgs) 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.