判断一个页面加载所耗费的时间

protected DateTime dt;
        protected void Page_Load(object sender, EventArgs e)
        {
           
        }
        protected override void OnPreInit(EventArgs e)
        {
            dt = DateTime.Now;
            base.OnPreInit(e);
        }

        protected override void OnLoadComplete(EventArgs e)
        {
            base.OnLoadComplete(e);
            TimeSpan ts = DateTime.Now - dt;
            Response.Write("加载页面用时：" + ts.TotalMilliseconds);
        }