[HttpPost]
        [ValidateAntiForgeryToken]
        public async Task<IActionResult> Login(LoginViewModel loginViewModel)
        {
            if (!ModelState.IsValid)
                return View(loginViewModel);

            var user = await _userManager.FindByNameAsync(loginViewModel.UserName);

            if (user == null)
            {
                ModelState.AddModelError(string.Empty, "The username does not exist.");
                return View(loginViewModel);
            }

            var role = await _userManager.IsInRoleAsync(user, Roles.Admin);

            if (!role)
            {
                ModelState.AddModelError(string.Empty, "You have no permission.");
                return View(loginViewModel);
            }

            var result = await _signInManager.PasswordSignInAsync(loginViewModel.UserName,
                loginViewModel.Password, true , lockoutOnFailure: false);

            if (result.Succeeded)
            {
                var claims = new[] {
                    new Claim(ClaimTypes.Role, Roles.Admin)
                };

                var principal = new ClaimsPrincipal(
                    new ClaimsIdentity(claims, CookieAuthenticationOptionsConstants.AuthenticationScheme));

                await HttpContext.Authentication.SignInAsync(CookieAuthenticationOptionsConstants.AuthenticationScheme,
                    principal,
                    new AuthenticationProperties { IsPersistent = true });

                return Redirect(loginViewModel.RedirectUrl);
            }

            if (result.IsLockedOut)
            {
                return this.RedirectToHome();
            }
            else
            {
                ModelState.AddModelError(string.Empty, "The username/password couple is invalid.");
                return View(loginViewModel);
            }
        }