public string SignInAjax(LoginViewModel model)
 {
     if (ModelState.IsValid)
     {
         var user = UserManager.Find(model.UserName, model.Password);
         if (user != null)
         {
             SignIn(user, true);
             return JsonConvert.SerializeObject(ModelState);
         }
         ModelState.AddModelError("CustomErrors", "E-mail і/або пароль невірні");
     }
     return JsonConvert.SerializeObject(ModelState);
 }
 public ActionResult SignIn(LoginViewModel loginViewModel, string returnUrl)
 {
     if (ModelState.IsValid)
     {
         var user = UserManager.Find(loginViewModel.UserName, loginViewModel.Password);
         if (user != null)
         {
             SignIn(user, true);
             return RedirectToLocal(returnUrl);
         }
         ModelState.AddModelError("", "E-mail і/або пароль невірні");
     }
     loginViewModel = new LoginViewModel() {UserName = loginViewModel.UserName};
     ModelState["Password"].Value = null;
     return View(loginViewModel);
 }