title: Html.RenderAction fails in page after RedirectToAction()
body: <p>I have a page "ViewUser". with this structure</p>
  
  <pre><code>//display something about the user
  @{Html.RenderAction("UpdateUser", new { UserId = @Model.UserId });}
  //display some more stuff
  </code></pre>
  
  <p>In the controller method for UpdateUser I have</p>
  
  <pre><code>public ActionResult UpdateUser(int UserId){//populate form vars
  [HttpPost]
  public ActionResult UpdateUser(User u)//
  // code to update the user
  return RedirectToAction("ViewUser", new { User = u.UserId });
  </code></pre>
  
  <p>When I open the page it works fine I see my user data and the date in the UpdateUser form.
  However when I update the user data and redirect to the ViewUser page from UpdateUser I get
  "Child actions are not allowed to perform redirect actions."</p>
  
  <p>but opening the page manually again show that the update was successful.
  As far as I understand the browser should be performing a new GET for everything so I don't understand why it works for a manual refresh but not when UpdateUser returns the redirect?</p>