The MouseWheelScrollLines property indicates how many lines to scroll, by default, in a multi-line control that has a scroll bar. The corresponding Platform SDK system-wide parameters are SPI_GETWHEELSCROLLLINES and SPI_SETWHEELSCROLLLINES. For more information about system-wide parameters, see "SystemParametersInfo" in the Platform SDK documentation at http://msdn.microsoft.com.
Be sure to handle the special case that occurs if the "One screen at a time" mouse option is selected. In this case, the MouseWheelScrollLines property has a value of -1.
Windows 8.1, Windows Server 2012 R2, Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)