https://msdn.microsoft.com/en-us/library/jj679962(v=vs.113).aspx
1.引用Entity Framework
2.Data Annotations
1)主键：[Key] 2.复合主键：多个[Key] 3.外键：[ForeignKey] 4.必须：[Required]
Entity Framework
原文：http://www.cnblogs.com/liandy0906/p/7135794.html
