ASP.NET MVC 3，代码优先EF：原始值？

Question

My code seems straightforward:

bool rv = false;
var results = from user in Users
            where user.userName.Equals(newUser.userName)
            select user;
if (results.Count() == 0)
{
    this.context.Users.Add(newUser);
    this.context.SaveChanges();
    rv = true;
}
return rv;

But this causes a DbEntityValidationException with an inner exception value that says: OriginalValues cannot be used for entities in the Added state.

...What does that even mean? The only thing I can think of is that newUser shows a value of 0 for userID even though this has a private setter and userID , as a primary key, is supposed to be database-generated. But if that were the problem, it would not be possible to simply use Add() to insert an object into any EF database ever. So I'm confused.

Thanks in advance to anyone who can help shed some light on this.

ETA: newUser is created by the following code in my Controller:

[HttpPost]
public ActionResult CreateRegistration(FormVMRegistration newRegistration)
{
    //draw info from form and add a new user to repository
    User newUser = new User();
    newUser.userName = newRegistration.userName;
    newUser.screenName = newRegistration.screenName;
    newUser.password = newRegistration.usersPW;

    bool addSuccess = userRep.Add(newUser);
    ...
}

FormVMRegistration is just a ViewModel with nothing but string properties, to convey data from the Regiostration form to the Controller. userRep is my User Repository.

Answer 1

I think it comes from the fact that you're using the newUser object before it is saved. Try to change this line

bool addSuccess = userRep.Add(newUser);

to

bool addSuccess = userRep.Add(newUser, newRegistration.userName);

and then (given passedUserName is a passed name from above) change your linq query to:

var results = from user in Users
        where user.userName.Equals(passedUserName)
        select user;

Good luck!

Answer 2

As near as can be determined, the problem seems to have stemmed from "deep" references to objects, or references to references. IOW, class Foo made a reference to class Bar which made a reference to class Baz which made a reference to class Foo... and apparently EF doesn't like this so much, because it's not easy to validate.