/// <summary>
        /// 指定header参数的HTTP Get方法
        /// </summary>
        /// <param name="headers"></param>
        /// <param name="url"></param>
        /// <returns>respondse</returns>
        public string Get(WebHeaderCollection headers, string url ,string responseEncoding="UTF-8",bool isUseCookie = false)
        {
            string responseText = "";
            try
            {
                var request = (HttpWebRequest)WebRequest.Create(url);
                    request.Method = "GET";
                foreach (string key in headers.Keys)
                {
                    switch (key.ToLower())
                    {
                        case "user-agent":
                            request.UserAgent = headers[key];
                            break;
                        case "referer":
                            request.Referer = headers[key];
                            break;
                        case "host":
                            request.Host = headers[key];
                            break;
                        case "contenttype":
                            request.ContentType = headers[key];
                            break;
                        case "accept":
                            request.Accept = headers[key];
                            break;
                        default:
                            break;
                    }
               }
                if (string.IsNullOrEmpty(request.Referer))
                {
                    request.Referer = "http://weixin.sogou.com/";
                };
                if (string.IsNullOrEmpty(request.Host))
                {
                    request.Host = "weixin.sogou.com";
                };
                if (string.IsNullOrEmpty(request.UserAgent))
                {
                    Random r = new Random();
                    int index = r.Next(WechatSogouBasic._agent.Count - 1);
                    request.UserAgent = WechatSogouBasic._agent[index];
                }
                if (isUseCookie)
                {
                    CookieCollection cc = Tools.LoadCookieFromCache();
                    request.CookieContainer = new CookieContainer();
                    request.CookieContainer.Add(cc);
                }
                HttpWebResponse response = (HttpWebResponse)request.GetResponse();
                if (isUseCookie && response.Cookies.Count >0)
                {
                    var cookieCollection = response.Cookies;
                    WechatCache cache = new WechatCache(Config.CacheDir, 3000);
                    if (!cache.Add("cookieCollection", cookieCollection, 3000)) { cache.Update("cookieCollection", cookieCollection, 3000); };
                }
                // Get the stream containing content returned by the server.
                Stream dataStream = response.GetResponseStream();
                //如果response是图片，则返回以base64方式返回图片内容，否则返回html内容
                if (response.Headers.Get("Content-Type") == "image/jpeg" || response.Headers.Get("Content-Type") == "image/jpg")
                {
                    Image img = Image.FromStream(dataStream, true);
                    using (MemoryStream ms = new MemoryStream())
                    {
                        // Convert Image to byte[]
                        //img.Save("myfile.jpg");
                        img.Save(ms,System.Drawing.Imaging.ImageFormat.Jpeg);
                        byte[] imageBytes = ms.ToArray();
                        // Convert byte[] to Base64 String
                        string base64String = Convert.ToBase64String(imageBytes);
                        responseText = base64String;
                    }
                }
                else //read response string
                {
                    // Open the stream using a StreamReader for easy access.
                    Encoding encoding;
                    switch (responseEncoding.ToLower())
                    {
                        case "utf-8":
                            encoding = Encoding.UTF8;
                            break;
                        case "unicode":
                            encoding = Encoding.Unicode;
                            break;
                        case "ascii":
                            encoding = Encoding.ASCII;
                            break;
                        default:
                            encoding = Encoding.Default;
                            break;
                               
                    }
                    StreamReader reader = new StreamReader(dataStream, encoding);//System.Text.Encoding.Default
                    // Read the content.
                    if (response.StatusCode == HttpStatusCode.OK)
                    {
                        responseText = reader.ReadToEnd();
                        if (responseText.Contains("用户您好，您的访问过于频繁，为确认本次访问为正常用户行为，需要您协助验证"))
                        {
                            _vcode_url = url;
                            throw new Exception("weixin.sogou.com verification code");
                        }
                    }
                    else
                    {
                        logger.Error("requests status_code error" + response.StatusCode);
                        throw new Exception("requests status_code error");
                    }
                    reader.Close();
                }

                dataStream.Close();
                response.Close();
            }
            catch (Exception e)
            {
                logger.Error(e);
            }
            return responseText;
        }

public List<OfficialAccount> SearchOfficialAccount(string keyword, int page = 1)
        {
            List<OfficialAccount> accountList = new List<OfficialAccount>();
            string text = this._SearchAccount_Html(keyword, page);//返回了一个搜索页面的html代码
            HtmlDocument pageDoc = new HtmlDocument();
            pageDoc.LoadHtml(text);
            HtmlNodeCollection targetArea = pageDoc.DocumentNode.SelectNodes("//ul[@class=‘news-list2‘]/li");
            if (targetArea != null)
            {
                foreach (HtmlNode node in targetArea)
                {
                    try
                    {
                        OfficialAccount accountInfo = new OfficialAccount();
                        //链接中包含了&amp; html编码符，要用htmdecode，不是urldecode
                        accountInfo.AccountPageurl = WebUtility.HtmlDecode(node.SelectSingleNode("div/div[@class=‘img-box‘]/a").GetAttributeValue("href", ""));
                        //accountInfo.ProfilePicture = node.SelectSingleNode("div/div[1]/a/img").InnerHtml;
                        accountInfo.ProfilePicture = WebUtility.HtmlDecode(node.SelectSingleNode("div/div[@class=‘img-box‘]/a/img").GetAttributeValue("src", ""));
                        accountInfo.Name = node.SelectSingleNode("div/div[2]/p[1]").InnerText.Trim().Replace("<!--red_beg-->", "").Replace("<!--red_end-->", "");
                        accountInfo.WeChatId = node.SelectSingleNode("div/div[2]/p[2]/label").InnerText.Trim();
                        accountInfo.QrCode = WebUtility.HtmlDecode(node.SelectSingleNode("div/div[3]/span/img").GetAttributeValue("src", ""));
                        accountInfo.Introduction = node.SelectSingleNode("dl[1]/dd").InnerText.Trim().Replace("<!--red_beg-->","").Replace("<!--red_end-->", "");
                        //早期的账号认证和后期的认证显示不一样？，对比 bitsea 和 NUAA_1952 两个账号
                        //现在改为包含该script的即认证了
                        if (node.InnerText.Contains("document.write(authname(‘2‘))"))
                        {
                            accountInfo.IsAuth = true;
                        }
                        else
                        {
                            accountInfo.IsAuth = false;
                        }
                        accountList.Add(accountInfo);
                    }
                    catch (Exception e)
                    {
                        logger.Warn(e);
                    }
                }
            }
            
          
            return accountList; 
        }