public void EditUser(User user)
        {
            var entry = _databaseModel.Entry(user);

            if (entry.State == EntityState.Detached)
            {
                var set            = _databaseModel.Set <User>();
                var attachedEntity = set.Find(user.UserId);  // You need to have access to key

                if (attachedEntity != null)
                {
                    var attachedEntry = _databaseModel.Entry(attachedEntity);
                    attachedEntry.CurrentValues.SetValues(user);
                }
                else
                {
                    entry.State = EntityState.Modified; // This should attach entity
                }
            }

            _databaseModel.SaveChanges();
        }