When handling the Control.MouseWheel event it is important to follow the user interface (UI) standards associated with the mouse wheel. The MouseEventArgs.Delta property value indicates the amount the mouse wheel has been moved. The UI should scroll when the accumulated delta is plus or minus 120. The UI should scroll the number of logical lines returned by the SystemInformation.MouseWheelScrollLines property for every delta value reached. You can also scroll more smoothly in smaller that 120 unit increments, however the ratio should remain constant, that is SystemInformation.MouseWheelScrollLines lines scrolled per 120 delta units of wheel movement.

For more information about handling mouse wheel messages, see the WM_MOUSEWHEEL message documentation in the MSDN library at http://msdn.microsoft.com/library.

Mouse events occur in the following order:

For more information about handling events, see Consuming Events.