Turn string into json C#

I have this sample code that i am working with. The json is a result of the http post.

var json = @"{'user': {
                        'country':'US',
                        'email':'[email protected]',
                        'first_name':'Test',
                        'last_name':'API',
                        'phone':null,
                        'zip':null,
                        'login_url':'https://new.site.com/xlogin/12325/abd9832cd92'
                        }
                    }";
        var jsonSerializer = new JavaScriptSerializer();
        var itemsList = (IDictionary<string, object>)jsonSerializer.DeserializeObject(json);
        var url = itemsList["user.login_url"];

On itemsList["user.login_url"] i am getting the following error:

 The given key was not present in the dictionary.
Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.

Exception Details: System.Collections.Generic.KeyNotFoundException: The given key was not present in the dictionary.

Source Error:


Line 545:        var jsonSerializer = new JavaScriptSerializer();
Line 546:        var itemsList = (IDictionary<string, object>)jsonSerializer.DeserializeObject(json);
Line 547:        var url = itemsList["user.login_url"];
Line 548:    }
Line 549:

Am i doing something wrong here? How should i access the first name, last name and url etc from this object?

Alternately, how can i tie this result to a class that has following properties? I just need a pointer to a good resource.

public class User
{
    public string Country { get; set; }
    public string Email { get; set; }
    public string FirstName { get; set; }
    public string LastName { get; set; }
    public string Phone { get; set; }
    public string Zip { get; set; }
    public string LoginUrl { get; set; }
}

Thanks.