China Union Pay helper

        static string proxyIpAddress = AppConfig.GetProxyIpAddress;
        static string proxyUserName = AppConfig.GetProxyUserName;
        static string proxyPassword = AppConfig.GetProxyPassword;

        static int _timeout = 100000;

        #region CUP Method
        /// <summary>
        /// 请求与响应的超时时间
        /// </summary>
        static public int Timeout
        {
            get { return _timeout; }
            set { _timeout = value; }
        }

        /// <summary>
        /// 执行HTTP POST请求。
        /// </summary>
        /// <param name="url">请求地址</param>
        /// <param name="parameters">请求参数</param>
        /// <returns>HTTP响应</returns>
        static public string DoPost(string url, IDictionary<string, string> parameters)
        {
            string result = string.Empty;
            try
            {
                HttpWebRequest req = GetWebRequest(url, "POST");

                NetworkCredential proxyCredential = new NetworkCredential();
                proxyCredential.UserName = proxyUserName;
                proxyCredential.Password = proxyPassword;
                req.Credentials = proxyCredential;

                WebProxy proxy = new WebProxy(proxyIpAddress);
                proxy.Credentials = proxyCredential;
                req.Proxy = proxy;

                var httpClientHandler = new HttpClientHandler()
                {
                    Proxy = proxy,
                };
                httpClientHandler.PreAuthenticate = true;
                httpClientHandler.UseDefaultCredentials = false;
                httpClientHandler.Credentials = proxyCredential;
                var client = new HttpClient(handler: httpClientHandler, disposeHandler: true);

                var res = client.GetStringAsync(url).Result;


                req.ContentType = "application/x-www-form-urlencoded;charset=utf-8";

                byte[] postData = Encoding.UTF8.GetBytes(BuildQuery(parameters));
                Stream reqStream = req.GetRequestStream();
                reqStream.Write(postData, 0, postData.Length);
                reqStream.Close();

                HttpWebResponse rsp = (HttpWebResponse)req.GetResponse();
                Encoding encoding = Encoding.GetEncoding(rsp.CharacterSet);
                result = GetResponseAsString(rsp, encoding);
            }
            catch (Exception ex)
            {
                result = string.Format("Request exception:{0}, please try again later.", ex.Message);
            }
            return result;
        }

        /// <summary>
        /// 执行HTTP GET请求。
        /// </summary>
        /// <param name="url">请求地址</param>
        /// <param name="parameters">请求参数</param>
        /// <returns>HTTP响应</returns>
        static public string DoGet(string url, IDictionary<string, string> parameters)
        {
            string result = string.Empty;
            try
            {
                if (parameters != null && parameters.Count > 0)
                {
                    if (url.Contains("?"))
                    {
                        url = url + "&" + BuildQuery(parameters);
                    }
                    else
                    {
                        url = url + "?" + BuildQuery(parameters);
                    }
                }

                HttpWebRequest req = GetWebRequest(url, "GET");
                req.ContentType = "application/x-www-form-urlencoded;charset=utf-8";

                HttpWebResponse rsp = (HttpWebResponse)req.GetResponse();
                Encoding encoding = Encoding.GetEncoding(rsp.CharacterSet);
                result = GetResponseAsString(rsp, encoding);
            }
            catch (Exception ex)
            {
                result = string.Format("Request exception:{0}, please try again later.", ex.Message);
            }
            return result;
        }

        static public HttpWebRequest GetWebRequest(string url, string method)
        {
            HttpWebRequest req = (HttpWebRequest)WebRequest.Create(url);
            req.ServicePoint.Expect100Continue = false;
            req.Method = method;
            req.KeepAlive = true;
            //req.UserAgent = "Aop4Net";
            req.Timeout = _timeout;
            return req;
        }

        /// <summary>
        /// 把响应流转换为文本。
        /// </summary>
        /// <param name="rsp">响应流对象</param>
        /// <param name="encoding">编码方式</param>
        /// <returns>响应文本</returns>
        static public string GetResponseAsString(HttpWebResponse rsp, Encoding encoding)
        {
            StringBuilder result = new StringBuilder();
            Stream stream = null;
            StreamReader reader = null;

            try
            {
                // 以字符流的方式读取HTTP响应
                stream = rsp.GetResponseStream();
                reader = new StreamReader(stream, encoding);

                // 按字符读取并写入字符串缓冲
                int ch = -1;
                while ((ch = reader.Read()) > -1)
                {
                    // 过滤结束符
                    char c = (char)ch;
                    if (c != '\0')
                    {
                        result.Append(c);
                    }
                }
            }
            finally
            {
                // 释放资源
                if (reader != null) reader.Close();
                if (stream != null) stream.Close();
                if (rsp != null) rsp.Close();
            }

            return result.ToString();
        }

        /// <summary>
        /// 组装普通文本请求参数用于post请求
        /// </summary>
        /// <param name="parameters">Key-Value形式请求参数字典</param>
        /// <returns>URL编码后的请求数据</returns>
        static public string BuildQuery(IDictionary<string, string> parameters)
        {
            StringBuilder postData = new StringBuilder();
            bool hasParam = false;

            IEnumerator<KeyValuePair<string, string>> dem = parameters.GetEnumerator();
            while (dem.MoveNext())
            {
                string name = dem.Current.Key;
                string value = dem.Current.Value;
                // 忽略参数名或参数值为空的参数
                if (!string.IsNullOrEmpty(name) && !string.IsNullOrEmpty(value))
                {
                    if (hasParam)
                    {
                        postData.Append("&");
                    }

                    postData.Append(name);
                    postData.Append("=");
                    postData.Append(Uri.EscapeDataString(value));
                    hasParam = true;
                }
            }

            return postData.ToString();
        }
        #endregion