Control. On Mouse Wheel(MouseEventArgs) MethodRaises the MouseWheel event. protected: override void OnMouseWheel(System::Windows::Forms::MouseEventArgs ^ e);protected override void OnMouseWheel (System. Windows. Forms. MouseEventArgs e);override this.OnMouseWheel : System. Windows. Forms. MouseEventArgs -> unitProtected Overrides Sub OnMouseWheel (e As MouseEventArgs) If the vertical scroll bar is visible, which means that the VScroll property is set totrue, the mouse wheel scrolls through the ScrollableControl control vertically. However, if only the horizontal scroll bar is visible, which means that the VScroll is set tofalse and the HScroll property to set totrue, the mouse wheel scrolls horizontally. Raising an event invokes the event handler through a delegate. For more information, see Handling and Raising Events. The OnMouseWheel 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.