Note that fixed rows are not supported in child row collections. Setting Fixed property to true on a child row will not actually fix the row. It will however add the row to the associated row collection's FixedRows collection (RowsCollection.FixedRows) and also apply any fixed row related appearances to it. It will also move the row to the beginning of the row collection. Also note that fixed rows are not supported in card-view.
Also note that when a fixed row is expanded any sibling fixed rows occuring after it will not be fixed. They will remain non-fixed until the expanded fixed row is collapsed. They will however remain in the FixedRows collection and keep their fixed row appearances.
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