ASP.NET MVC - How to maintain ModelState from a different controller?

Question

I have a HomeController with an Index action that shows the Index.aspx view. It has a username/password login section. When the user clicks the submit button, it POSTs to a Login action in the AccountController.

        <% Html.BeginForm("Login", "Account", FormMethod.Post); %>

In that action, it tests for Username/Password validity and if invalid, sends the user back to the Login page with a message that the credentials were bad.

    [HttpPost]
    public ActionResult Login(LoginViewModel Model, string ReturnUrl)
    {
        User user = MembershipService.ValidateUser(Model.UserName, Model.Password);
        if (user != null)
        {
            //Detail removed here
            FormsService.SignIn(user.ToString(), Model.RememberMe);
            return Redirect(ReturnUrl);
        }
        else
        {
            ModelState.AddModelError("", "The user name or password provided is incorrect.");
        }
        // If we got this far, something failed, redisplay form
        return RedirectToAction("Index", "Home");  // <-- Here is the problem.  ModelState is lost.
    }

But here's the problem: the ValidationSummary is always blank because we're losing the Model when we RedirectToAction.

So the question is: How do I send the user to the action on a different controller without a Redirect?

Answer 1

As others have said it's common to return the view if validation fails but as you are calling from your account controller you will want to specify the full path of your view

return View("~/Views/Home/Index.aspx", model);

Or

It is also common to have a seperate login page and redirect to that page if the login fails. Both pages will submit to the same login action. Facebook does this for example.

Or

As you only want to display an error message

return RedirectToAction("Index", "Home", new { LoginAttempts = 1 });

then in your Index action read the LoginAttempts parameter and choose to display the error message accordingly.

Answer 2

Use TempData to save state between requests. Use special attributes for convenience as shown here.

Few moments to mention:

• Don't return View directly from your POST-action, respect Post-Redirect-Get pattern.
• Don't overuse TempData. It's only supposed to save model state right before redirect and to retrieve it right after being redirected.