TryUpdateModel() An item with the same key has already been added
<p>Project works fine in VS 2008 without erors, app is runing fine!!
 I have opened project in VS 2010 , no errors, have tried to run applicatin and on user login. I am calling TryUpdateModel(User)  </p>

<pre><code>public ActionResult Login(FormCollection form)
        {
            User usr= new User();
            TryUpdateModel(usr); // Here is an error.
if (!ValidateLogOn(usr.Username, usr.Password))
            {
                return View(usr);
            }
}
// user class
    public class User : MembershipUser
        {
            public long UserID { get; set; }
            public string Username { get; set; }
            public string Password { get; set; }       
            public long SomeOtehrID{ get; set; }
        }
</code></pre>

<p>And get the ArgumentException. I am using MVC 1.0 Sorry for such little informatin , but I have now clue what is going on... Or how to debug this. </p>

<p>Please, any help advice (rope) is welcome.</p>