我有两个完全相同的数据库表，一个 prod 和一个 dev。每当我部署到开发数据库时，一切正常。prod 数据库允许我尝试使用 EF 和 MVC 将数据写回数据库时引发此错误。
System.InvalidOperationException: The operation failed: The relationship could not be changed because one or more of the foreign-key properties is non-nullable. When a change is made to a relationship, the related foreign-key property is set to a null value. If the foreign-key does not support null values, a new relationship must be defined, the foreign-key property must be assigned another non-null value, or the unrelated object must be deleted.
at System.Data.Objects.ObjectContext.SaveChanges(SaveOptions options)
at System.Data.Entity.Internal.InternalContext.SaveChanges()
当然，我已经检查了这个http://blogs.msdn.com/b/dsimmons/archive/2010/01/31/deleting-foreign-key-relationships-in-ef4.aspx
似乎我的 EF 代码没有问题，纯粹是 db 表问题无论如何我可以找到更多详细信息吗？