If startDate or endDate falls within the range of an existing DateRange in the collection, that DateRange is updated to include the new dates, and that instance is returned. If the range defined by startDate and endDate is completely outside the range defined by any existing members, a new DateRange instance is created to describe the added range.
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