public ActionResult Edit(UserViewModel input)
        {
            try
            {
                users.First(x => x.Id == input.Id).FirstName = input.FirstName;
                users.First(x => x.Id == input.Id).LastName = input.LastName;
                users.First(x => x.Id == input.Id).Email = input.Email;

                var viewModel = users.First(x => x.Id == input.Id);
                var updateSucced = new
                {
                    html = RenderPartialViewToString("_Details", viewModel),
                    message = "User details has been updated"
                };
                return Json(updateSucced);
            }
            catch
            {
                var updateFailed = new
                {
                    messageError = "update item failed"
                };
                return Json(updateFailed);
            }
        }
 public UserController()
 {
     if (users == null) {
         users = new List<UserViewModel>();
         var user1 = new UserViewModel();
         user1.Id = Guid.NewGuid();
         user1.FirstName = "David";
         user1.LastName = "Beckham";
         user1.Email = "*****@*****.**";
         var user2 = new UserViewModel();
         user2.Id = Guid.NewGuid();
         user2.FirstName = "Eric";
         user2.LastName = "Cantona";
         user2.Email = "*****@*****.**";
         users.Add(user1);
         users.Add(user2);
     }
 }