/// <summary>
        /// 获取网页源代码
        /// </summary>
        public static HtmlDocument GetHtmlSourceCode(string url, ProxyTuple proxy = null)
        {
            if (string.IsNullOrWhiteSpace(url))
            {
                return(null);
            }
            HtmlDocument document = null;

            Console.WriteLine("Get html source code from {0}", url);
            var webClient = new HtmlWeb
            {
                UserAgent = "User-Agent:Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/39.0.2171.71 Safari/537.36"
            };

            try
            {
                document = proxy == null?webClient.Load(url) : webClient.Load(url, proxy.Host, proxy.Port, proxy.UserId, proxy.Password);
            }
            catch
            {
                Console.WriteLine("An error appear when getting source code of {0}", url);
                return(null);
            }
            return(document);
        }
        /// <summary>
        /// 添加代理
        /// </summary>
        public static void AddInto(ProxyTuple newProxy)
        {
            ProxyTuple oldProxy;

            newProxy.Useful = true;
            if ((oldProxy = bagProxys.FirstOrDefault(item => item.Host == newProxy.Host)) != null)
            {
                oldProxy.Port     = newProxy.Port;
                oldProxy.UserId   = newProxy.UserId;
                oldProxy.Password = newProxy.Password;
            }
            else
            {
                newProxy.Index = bagProxys.Count;
                bagProxys.Add(newProxy);
            }
        }