如何添加或删除多对多关系，与实体的框架，通过实体的钥匙吗？

Question

我试过:

using (Entities e = new Entities())
{
    EntityKey key = new EntityKey("Entities.Users", "UserId", 20);
    User user = new User { EntityKey = key};
    Role role = e.Roles.FirstOrDefault();
    //role.Users.Attach(user); //throws (when uncommented...) InvalidOperationException:
    //The object being attached to the source object is not attached to the same ObjectContext as the source object.
    role.Users.Add(user); //throws InvalidOperationException too:
    //The object cannot be added to the ObjectStateManager because it already has an EntityKey. Use ObjectContext.Attach to attach an object that has an existing key.
    e.SaveChanges();
}

当试图使用Remove()而不调用附加前没有异常，但有关不删除。

Answer 1

试试这样的事情：

User user = new User {UserId = 20};
e.AttachTo("Users", user);
Role role = e.Roles.FirstOrDefault();
role.Users.Add(user);
e.SaveChanges();

我发现它很容易的工作与短的实体(如上述用户)，而不是EntityKeys.

看看这个 博客 更多信息Stub实体的技术。

希望这可以帮助

亚历克斯