https://msdn.microsoft.com/zh-cn/library/system.componentmodel.dataannotations.aspx
http://www.cnblogs.com/9988/archive/2012/04/25/2469838.html
实例：
http://blog.csdn.net/hwt0101/article/details/8588846
http://www.cnblogs.com/lgzslf/archive/2011/08/04/2127409.html
http://www.cnblogs.com/fuchongjundream/p/3844051.html
