MVC4 Session not persisted between requests

Question

BIG update after some good testing

I have a MVC4 web application and I'm simply debugging it in visual studio 2010 just to learn some more about webdevelopment (and MVC in particular). I'm playing with Session now. But I don't understand why I lose my variables after a new httprequest.

It's like this question: Losing my session variables

My web.config for the session part looks like:

<sessionState mode="InProc"
   cookieless="false"
   timeout="20"/>

My little test project to isolate the problem works fine and looks like:

Controllers - HomeController

public class HomeController : Controller
{
    //
    // GET: /Test/

    public ActionResult Index()
    {
        string t = (string)Session["Test1"];
        ViewBag.Result = t;
        return View();
    }

}

• MysessionController

  public class MysessionController : Controller { // // GET: /Mysession/

      public ActionResult Index()
      {
          return View(new Models.Mysession() {ID = Session.SessionID});
      }
  
      [HttpPost]
      public ActionResult Index(Models.Mysession mySession) {
          Session["Test1"] = "Bla";
          return RedirectToAction("Index", "Home");
      }
  
  }
  

Models

public class Mysession {
    [Required]
    public string ID { get; set; }
}

Views

• Home

  • Index.cshtml

    @{ ViewBag.Title = "Index"; }

    Index

    @@ViewBag.Result@ @((string)Session["Test1"]) @Html.ActionLink("My session", "Index", "Mysession")

• Mysession

  • Index.cshtml

    @model SessionTest.Models.Mysession @{ ViewBag.Title = "Index"; }

  Index

  @using (Html.BeginForm()) {

  @Html.ValidationSummary(false)
  <fieldset>
      <legend>Mysession</legend>
       <div class="editor-label">
          @Html.LabelFor(model => model.ID)
      </div>
      <div class="editor-field">
          @Html.EditorFor(model => model.ID)
      </div>
      <p>
          <input type="submit" value="Log in" />
      </p>
  </fieldset>
  

  }

This looks in a nutshell like my main application, the DIFFERENCE is: In MysessionController in the HTTPPOST Index action where the session variable is set I acces a XML file to look up something.

The XML file is my persistent storage because I don't have a SQL server. My question is, can this affect my session?

If so, I would like to point out that I acces the XML file PRIOR to setting the variable in the session. So it seems strange to me. But I've pinpointed by testing that if I don't acces the XML file then the vars in the session are fine. If I acces the XML file the vars in the session are null after the RedirectToAction.

I don't know why I didn't came to this conclusion yesterday. Sorry everybody. I did some sloppy testing yesterday.

Answer 1

First off, I would like to thank everybody that has put time in this question. After I got myself together and finally conducted a proper test I pinpointed the problem to accessing a XML file on the hard drive. Don't know what I was messing about yesterday...

I found trough Google several posts and articles about losing your session after accessing files. Like this one:

http://blogs.msdn.com/b/tess/archive/2006/08/02/asp-net-case-study-lost-session-variables-and-appdomain-recycles.aspx

Fantastic case study by Tessa Ferrandez. And to lesser extend: http://forums.asp.net/t/998370.aspx/1

And:

http://blogs.msdn.com/b/toddca/archive/2005/12/01/499144.aspx

Conclusion

When you access files in any way of your website the AppDomain will be refreshed and this will refresh your session.

Never put a file you need to access through your website in your 'bin' folder. I've moved my XML file to App_Data and the variables are persisted in the Session.

Summed up my answer on my blog: http://dannyvanderkraan.wordpress.com/2013/08/21/losing-session-variables-with-asp-net/