public class MvcApplication : System.Web.HttpApplication
    {
        protected void Application_Start()
        {
            AreaRegistration.RegisterAllAreas();
            FilterConfig.RegisterGlobalFilters(GlobalFilters.Filters);
            RouteConfig.RegisterRoutes(RouteTable.Routes);
            BundleConfig.RegisterBundles(BundleTable.Bundles);
            Application["OnlineUser"] = 0;
        }
        protected void Session_Start()
        {
            Application.Lock();
            Application["OnlineUser"] = (int) Application["OnlineUser"] + 1;
            Application.UnLock();
        }
        protected void Session_End()
        {
            Application.Lock();
            Application["OnlineUser"] = (int)Application["OnlineUser"] - 1;
            Application.UnLock();
        }
    }