C# 获取页面的响应时间

HttpWebRequest 请求：
DateTime start_time = DateTime.Now;

            try
            {
                HttpWebRequest webrequest = (HttpWebRequest)HttpWebRequest.Create("访问地址");
                HttpWebResponse webresponse = (HttpWebResponse)webrequest.GetResponse();
                if (webresponse.StatusCode == HttpStatusCode.OK)
                {
                    DateTime end_time = DateTime.Now;
                    TimeSpan ts = end_time - start_time;
                    int ch = (int)ts.TotalMilliseconds;//响应时间.(毫秒)
        	 }
            }

用WebBrowser打开：
为WebBrowser添加Navigating和DocumentCompleted事件.
分别在两个方法中记录当前时间.最后用DocumentCompleted-Navigating的时间差即为响应时间