依赖属性(Dependency Property)和附加属性(Attached Property)
参考
http://www.cnblogs.com/KevinYang/archive/2010/03/28/1699083.html
http://www.cnblogs.com/pszw/archive/2012/01/06/2312269.html
http://www.cnblogs.com/liping13599168/archive/2010/05/07/1729357.html