public async Task <IActionResult> DeclineClient(string id)
        {
            try
            {
                if (string.IsNullOrEmpty(id))
                {
                    throw new DBConcurrencyException();
                }

                var user = await _userHelper.GetUserByGuidIdAsync(id);

                if (user == null)
                {
                    return(new NotFoundViewResult("_Error404"));
                }

                var result = await _userHelper.DeleteUserAsync(user);

                if (!result.Success)
                {
                    throw new DBConcurrencyException();
                }

                _mailHelper.SendRefuseClient(user.Email, user.Name);

                await _notificationRepository.DeleteAsync(await _notificationRepository.GetByGuidIdAsync(user.GuidId));

                return(RedirectToAction(nameof(ListUsers)));
            }
            catch (DBConcurrencyException)
            {
                return(new NotFoundViewResult("_Error404"));
            }
            catch (Exception)
            {
                return(new NotFoundViewResult("_Error500"));
            }
        }