protected void Application_AcquireRequestState(object sender, EventArgs e)
        {
            var httpContext = HttpContext.Current;
            var session = httpContext.Session;

            if (User.Identity.IsAuthenticated && session["UserRole"]==null) {
                var identity = new GenericIdentity(string.Empty, string.Empty);
                httpContext.User = new GenericPrincipal(identity, new string[] { });
                FormsAuthentication.SignOut();
                Session.Clear();
            }
            else if ( session["UserRole"] != null)
                switch ((UserRoles)session["UserRole"])
                {
                    case UserRoles.Adminstrator:
                        httpContext.User = new GenericPrincipal(httpContext.User.Identity, new[] {"Administrator"});
                        break;
                    case UserRoles.Customer:
                        httpContext.User = new GenericPrincipal(httpContext.User.Identity, new[] {"Customer"});
                        break;
                    case UserRoles.Client:
                        httpContext.User = new GenericPrincipal(httpContext.User.Identity, new[] {"Client"});
                        break;
                }
        }