获得页面输出结果

protected override void Render(HtmlTextWriter writer)
    {
        Stopwatch stopwatch = new Stopwatch();
        stopwatch.Reset();
        stopwatch.Start();
        try
        {
            //会把页面的输出结果存储在这个StringBuilder中
            StringBuilder sb = new StringBuilder();
            StringWriter sw = new StringWriter(sb);
            HtmlTextWriter htw = new HtmlTextWriter(sw);
            base.Render(htw);
            string content = sb.ToString();

            //重新写入页面
            writer.Write(content);

        }
        catch (Exception ex)
        {
            Response.Write(ex.ToString());
            Response.End();
        }
        finally
        {
            stopwatch.Stop();
            Response.Write("runtime:" + stopwatch.ElapsedMilliseconds.ToString() + "ms");
        }
    }