Note that this property doesn't indicate whether the activity is presently visible in the UI. It indicates whether the activity will be displayed in the UI when the containing date range is displayed in a schedule control.
Target Platforms: Windows 10, Windows 8.1, Windows 8, Windows 7, Windows Server 2012, 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