public async Task<ActionResult> Adjust(UserBalanceAdjust adjustment)
        {
            if (!ModelState.IsValid)
                return View(adjustment);

            var user = await _userManager.FindByIdAsync(adjustment.UserId);
            if (user == null)
            {
                ModelState.AddModelError("UserId", "Cannot find user");
                return View(adjustment);
            }

            var result = _trnxService.AdjustBalance(user, adjustment.Amount, adjustment.Reason);

            if (!result.Success)
            {
                foreach (var err in result.Errors)
                    ModelState.AddModelError("", err);

                return View(adjustment);
            }

            _uow.SaveChanges();

            return RedirectToAction("Detail", "UserManagement", new { Id = adjustment.UserId });
        }
        public async Task<ActionResult> Adjust(int id)
        {
            var user = await _userManager.FindByIdAsync(id);
            if (user == null)
                return HttpNotFound();

            var model = new UserBalanceAdjust()
            {
                UserId = user.Id,
                UserName = user.UserName,
                CurrentBalance = user.Money,
            };

            return View(model);
        }