LoginMethods.cs

       [HttpGet]
        public IActionResult Login()
        {
            return View();
        }

        [HttpPost]
        public async Task<IActionResult> Login(UserRegisterModel model)
        {
            var exists = _db.Users.SingleOrDefault(u => u.Email.Equals(model.Username));
            if (exists != null)
                return View();

            var user = _db.Users.SingleOrDefault(u => u.UserName == model.Username);

            var result = await _signInManager.PasswordSignInAsync(user, model.Password, true, false);

            if (result.Succeeded)
            {
                return RedirectToAction("Index", "Home");
            }

            return View();
        }