title: Changing a Model's value in httppost action
body: <p>I'm looking to change the value of a string in a view model in the controller and pass it back to the view like so:</p>
  
  <pre><code>[HttpPost]
  public ActionResult TestAction(TestViewModel model)
  {
      model.TestStringValue = "test val";
      return View("Index", model);
  }
  </code></pre>
  
  <p>The value is shown in a textbox but isn't showing the updated value. What do I need to do in the controller to update a view model's field? </p>