public void OnAuthorization(AuthorizationContext ac)
        {
            bool         isAuthOK     = false;
            StaffService staffService = new StaffService();

            if (ac.HttpContext.Session["sessionId"] != null)
            {
                string  sessionId = ac.HttpContext.Session["sessionId"].ToString();
                StaffEF staff     = staffService.FindStaffBySessionId(sessionId);

                if (staff != null)
                {
                    isAuthOK = true;
                }
            }

            if (!isAuthOK)
            {
                ac.Result = new RedirectToRouteResult(
                    new RouteValueDictionary {
                    { "controller", "Login" },
                    { "action", "Index" }
                });
            }
        }