public ActionResult LogIn(string returnUrl)
 {
     var model = new LoginModel
     {
         ReturnUrl = returnUrl
     };
     return View(model);
 }
        public async Task<ActionResult> LogIn(LoginModel model)
        {
            if (!ModelState.IsValid)
            {
                return View();
            }

            var user = await _userManager.FindAsync(model.Email, model.Password);
            if (user != null)
            {
                var identity = await _userManager.CreateIdentityAsync(user, DefaultAuthenticationTypes.ApplicationCookie);

                GetAuthenticationManager().SignIn(identity);

                return Redirect(GetRedirectUrl(model.ReturnUrl));
            }

            ModelState.AddModelError("", "invalid email or password");
            return View();
        }