FormatString property is used to specify the format with which to format the value for displaying purposes when the control doesn't have focus. When the control has focus, InputMask is used. If this property is not specified then InputMask is used as well.
Target Platforms: Windows 10, Windows 8.1, Windows 8, Windows 7, Windows Server 2012, Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2