global.asax.cs

        protected void Application_PreRequestHandlerExecute()
        {
            if (!(Context.Handler is IRequiresSessionState)) return;

            var authenticationCookie = Request.Cookies[FormsAuthentication.FormsCookieName];
            if (authenticationCookie == null) return;

            var authenticationTicket = FormsAuthentication.Decrypt(authenticationCookie.Value);
            if (authenticationTicket == null || authenticationTicket.Expired) return;

            if (Membership.GetUser() != null) return;

            FormsAuthentication.SignOut();
            Response.Redirect(FormsAuthentication.LoginUrl, true);
        }