EF外键属性不可为空

Question

我有两个完全相同的数据库表，一个是prod，一个是dev。每当我部署到dev数据库时，一切都运行得很好。prod数据库允许我抛出这个错误，因为我尝试使用EF和MVC将数据写回数据库。

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，我已经检查过这个http://blogs.msdn.com/b/dsimmons/archive/2010/01/31/deleting-foreign-key-relationships-in-ef4.aspx

看起来我的EF代码没有问题，纯粹的数据库表问题，我可以找到更多的细节？

Answer 1

issue http://blogs.msdn.com/b/dsimmons/archive/2010/01/31/deleting-foreign-key-relationships-in-ef4.aspx上的一篇很好的文章《在EF4中删除外键关系》