I was playing around with SurfaceControllers and noticed that when I turned off JavaScript in my browser that my form no longer worked as expected. The form would post with the fields I entered, would go through the validation logic, ModelState would be set, RedirectToCurrentUmbracoPage() is called, and then I am presented with a blank form and no error messages.

The only thing I could think of was that during the umbraco.tv SurfaceController series, Tim used TempData to send a success flag back to the View. This seems to indicate that the page is redirecting and that the ModelState would not be available for the current request.

Using that theory I stored the ModelState and Model in TempData and loaded it in the initial view like so:

public ActionResult Index()
{
    ContactFormModel model = new ContactFormModel();
    if (TempData["Model"] != null)
        model = TempData["Model"] as ContactFormModel;
    if (TempData["ModelState"] != null && !ModelState.Equals(TempData["ModelState"]))
        ModelState.Merge((ModelStateDictionary)TempData["ModelState"]);
    return PartialView("ContactForm", model);
}

[HttpPost]
public ActionResult Submit(ContactFormModel model)
{
    if (ModelState.IsValid)
    {
        // Send email
        TempData["success"] = true;
    }
    else
    {
        TempData["ModelState"] = ModelState;
        TempData["Model"] = model;
    }
    return RedirectToCurrentUmbracoPage();
}

Is this currently the best way to handle this? Or is there a helper hidden somewhere that I can use to persist the model state? If not, might I recommend creating another RedirectToCurrentUmbracoPage variant that takes the ModelState as a parameter, and create another helper to load it into the initial view?