A summary task is defined as any task whose Tasks collection contains one or more members. A summary task is depicted differently in the user interface as well; by default it appears as a timeline with down-facing arrows at the beginning and end, to denote that it encompasses one or more tasks.
When a task becomes a summary, its StartDateTime and EndDateTime properties can no longer be changed, since at that point they represent the beginning of the earliest subtask, and the end of the latest sub-task.
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