public IActionResult IsIdAvailable(RemoteAttributeUser user)
 {
     return Json(data: string.Format(
         "/Area2/RemoteAttribute_Verify/IsIdAvailable rejects '{0}' with '{1}', '{2}', and '{3}'.",
         user.UserId4,
         user.UserId1,
         user.UserId2,
         user.UserId3));
 }
        public IActionResult Create(RemoteAttributeUser user)
        {
            if (!ModelState.IsValid)
            {
                return View(user);
            }

            _user = user;
            return RedirectToAction(nameof(Details));
        }