gistfile1.cs

public class Response_User
    {
        public int Id { get; set; }
        
        [ScaffoldColumn(false)]
        public virtual Response Response { get; set; }

        [ScaffoldColumn(false)]
        public virtual User User { get; set; }

        public User U
        {
            get
            {
                return DefaultTranslationOf<Response_User>.Property(r => r.User).Is(r => r.User).Evaluate(this);
            }
        }
    }

> Response_User ru = context.Response_Users.Where(r => r.U.Equals(user)).WithTranslations().SingleOrDefault(r => r.Survey.Id == Id);
The specified type member 'U' is not supported in LINQ to Entities. Only initializers, entity members, and entity navigation properties are supported.