The value of this field depends on the message. Use the LParam field to get information that is important for handling the message. LParam is typically used to store an object if it is needed by the message. Use the GetLParam method to retrieve and convert information from the LParam field into an object.
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)