public ActionResult logout()
    {
        Session.Clear();
        Session.Abandon();
        Session.RemoveAll();

        FormsAuthentication.SignOut();


        this.Response.Cache.SetExpires(DateTime.UtcNow.AddMinutes(-1));
        this.Response.Cache.SetCacheability(HttpCacheability.NoCache);
        this.Response.Cache.SetNoStore();          

        return RedirectToAction("Login");
    }