title: RedirectToAction after validation errors
body: <p>If I have the usual Edit actions, one for GET to retrieve an object by it's ID and to display it in an edit form. The next for POST to take the values in the ViewModel and update the object in the database.</p>
  
  <pre><code>public virtual ActionResult Edit(int id)
  
  [HttpPost]
  public ActionResult Edit(VehicleVariantEditSaveViewModel viewModel)
  </code></pre>
  
  <p>If an error occurs during model binding in the POST action, I understand I can RedirectToAction back to the GET action and preserve the ModelState validation errors by copying it to TempData and retrieving it after the redirect in the GET action.</p>
  
  <pre><code>if (TempData["ViewData"] != null)
  {
      ViewData = (ViewDataDictionary)TempData["ViewData"];
  }
  </code></pre>
  
  <p>How do I then convert that ViewData, which includes the previous invalid ModelState, into a new model to send to the view so the user sees their invalid input with validation warnings? Oddly enough if I pass in a new instance of my ViewModel retrieved from the database (with the original valid data) to the View() this is ignored and the (invalid) data in the ViewData is displayed! </p>
  
  <p>Thanks</p>