title: Writing files in App_Data causes tempdata to be null
body: <p>I have a small asp.net MVC 1 web app that can store files and create directories in the App_Data directory. When the write operation succeeds, I add a message to the tempdata and do a redirectToRoute. The problem is that the tempdata is null when the action is executed. If i write the files in a directory outside of the web applications root directory, the tempdata is not null and everything works correctly. Any ideas why writing in the app_data seems to clear the tempdata ?</p>
  
  <p>edit:
  if DRS.Logic.Repository.Manager.CreateFile(path, hpf, comment) writes in the App_Data, TempData will be null in the action being redirected to. if it is a directory out of the web app root it is fine. No exceptions are being thrown.</p>
  
  <pre><code>[AcceptVerbs(HttpVerbs.Post)]
  public ActionResult Create(int id, string path, FormCollection form)
  {
      ViewData["path"] = path;
      ViewData["id"] = id;
  
      HttpPostedFileBase hpf;
  
      string comment = form["FileComment"];
      hpf = Request.Files["File"] as HttpPostedFileBase;
  
      if (hpf.ContentLength != 0)
      {
          DRS.Logic.Repository.Manager.CreateFile(path, hpf, comment);
          TempData["notification"] = "file was created";
          return RedirectToRoute(new { controller = "File", action ="ViewDetails", id = id, path = path + Path.GetFileName(hpf.FileName) });
      }
      else
      {
          TempData["notification"] = "No file were selected.";
          return View();
      }
  }
  </code></pre>