asp.net 设置网页过期

        /// <summary>
        /// 判断网页是否过期
        /// </summary>
        /// <returns></returns>
        private bool isPageExpired()
        {
            if (Session["TimeStamp"] == null ||
               ViewState["TimeStamp"] == null)
                return false;
            else if (Session["TimeStamp"] == ViewState["TimeStamp"])
                return true;
            else
                return false;
        }

        protected void Page_Load(object sender, EventArgs e)
        {
            #region 判断网页是否过期

            Response.Cache.SetCacheability(HttpCacheability.NoCache);
            Response.Cache.SetExpires(DateTime.Now.AddSeconds(-));
            Response.Cache.SetNoStore();
            Response.AppendHeader("Pragma", "no-cache");
            if (Page.IsPostBack)
            {
                if (isPageExpired())
                {
                    Response.Redirect("expired.htm");
                    return;
                }
                else
                {
                    Session["TimeStamp"] = DateTime.Now.ToString();
                    ViewState["TimeStamp"] = DateTime.Now.ToString();
                }
            }

            #endregion
         }