/// <summary>   
    /// 取得HTML中所有图片的 URL。   
    /// </summary>   
    /// <param name="sHtmlText">HTML代码</param>   
    /// <returns>图片的URL列表</returns>   
    public static string[] GetHtmlImageUrlList(string sHtmlText)   
    {   
      // 定义正则表达式用来匹配 img 标签   
      Regex regImg = new Regex(@"<img\b[^<>]*?\bsrc[\s\t\r\n]*=[\s\t\r\n]*[""']?[\s\t\r\n]*(?<imgUrl>[^\s\t\r\n""'<>]*)[^<>]*?/?[\s\t\r\n]*>",   RegexOptions.IgnoreCase);   
        
      // 搜索匹配的字符串   
      MatchCollection matches = regImg.Matches(sHtmlText);   
      int i = 0;   
      string[] sUrlList = new string[matches.Count];   
        
      // 取得匹配项列表   
      foreach (Match match in matches)   
      sUrlList[i++] = match.Groups["imgUrl"].Value;   
      return sUrlList;   
    }  

public ActionResult GetQrcodeUrl()
        {
            string turn_url = Fetch.Query("turn_url");
            if (string.IsNullOrEmpty(turn_url))
            {
                turn_url = "http://ttyouni.com/wclogin/index";
            }
            turn_url = turn_url.Replace(":", "%3a").Replace("/", "%2f");
            string url = string.Format("https://open.weixin.qq.com/connect/qrconnect?appid={0}&redirect_uri={1}&response_type=code&scope=snsapi_login&state={2}#wechat_redirect", AppID, turn_url, "11111");
            string result = NetHelper.HttpGet(url);
            Regex regImg = new Regex(@"<img\b[^<>]*?\bsrc[\s\t\r\n]*=[\s\t\r\n]*[""']?[\s\t\r\n]*(?<imgUrl>[^\s\t\r\n""'<>]*)[^<>]*?/?[\s\t\r\n]*>", RegexOptions.IgnoreCase);
            string result_url = "https://open.weixin.qq.com" + regImg.Match(result).Groups["imgUrl"].Value;
            return Json(new { url = result_url }, JsonRequestBehavior.AllowGet);
        }