AppearanceHolder is used internally by a class that will expose one or more Appearance properties and an Appearances collection. During serialization the AppearanceHolder will serialize either the Appearance object or, if the Appearance is a member of the collection, its key or id. This is because the Appearance object will get serialized as part of the collection.
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
