public void DownloadImage(string url, string path)
        {
 
            HttpWebRequest req = (HttpWebRequest)WebRequest.Create(url);
 
            req.ServicePoint.Expect100Continue = false;
            req.UserAgent = "Mozilla/6.0 (MSIE 6.0; Windows NT 5.1; Natas.Robot)";
 
            req.Method = "GET";
            //req.Headers.Add("Cookie", "_sessionID=9FBCB4630D3F4D04955FEA7FBF725533; JSESSIONID=0000YTOL3mownFwgaoun0nHB_gu:-1");
            req.KeepAlive = true;
 
            
 
            HttpWebResponse rsp = (HttpWebResponse)req.GetResponse();
 
            System.IO.Stream stream = null;
 
            try
            {
 
                // 以字符流的方式读取HTTP响应
 
                stream = rsp.GetResponseStream();
 
                Image.FromStream(stream).Save(path);
 
            }
 
            finally
            {
 
                // 释放资源
 
                if (stream != null) stream.Close();
 
                if (rsp != null) rsp.Close();
 
            }
 
        }