public static string Post(string url, string data, Encoding encoding)
        {
            try
            {
                HttpWebRequest req = WebRequest.CreateHttp(new Uri(url));
                req.ContentType = "application/x-www-form-urlencoded;charset=utf-8";
                req.Method = "POST";
                req.Accept = "text/xml,text/javascript";
                req.ContinueTimeout = 60000;

                byte[] postData = http://www.mamicode.com/encoding.GetBytes(data);"&");
                    }

                    query.Append(name);
                    query.Append("=");
                    query.Append(WebUtility.UrlEncode(value));
                    hasParam = true;
                }
            }

            return query.ToString();
        }

        public static string GetResponseAsString(HttpWebResponse rsp, Encoding encoding)
        {
            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);
                return reader.ReadToEnd();
            }
            finally
            {
                // 释放资源
                if (reader != null) reader.Dispose();
                if (stream != null) stream.Dispose();
                if (rsp != null) rsp.Dispose();
            }
        }

        public static string GetAlidayuSign(IDictionary<string, string> parameters, string secret, string signMethod)
        {
            //把字典按Key的字母顺序排序
            IDictionary<string, string> sortedParams = new SortedDictionary<string, string>(parameters, StringComparer.Ordinal);

            //把所有参数名和参数值串在一起
            StringBuilder query = new StringBuilder();
            if (Constants.SIGN_METHOD_MD5.Equals(signMethod))
            {
                query.Append(secret);
            }
            foreach (KeyValuePair<string, string> kv in sortedParams)
            {
                if (!string.IsNullOrEmpty(kv.Key) && !string.IsNullOrEmpty(kv.Value))
                {
                    query.Append(kv.Key).Append(kv.Value);
                }
            }

            //使用MD5/HMAC加密
            if (Constants.SIGN_METHOD_HMAC.Equals(signMethod))
            {
                return Hmac(query.ToString(), secret);
            }
            else
            {
                query.Append(secret);
                return Md5(query.ToString());
            }
        }

        public static string Hmac(string value, string key)
        {
            byte[] bytes;
            using (var hmac = new HMACMD5(Encoding.UTF8.GetBytes(key)))
            {
                bytes = hmac.ComputeHash(Encoding.UTF8.GetBytes(value));
            }
            StringBuilder result = new StringBuilder();
            foreach (byte t in bytes)
            {
                result.Append(t.ToString("X2"));
            }
            return result.ToString();
        }

        public static string Md5(string value)
        {
            byte[] bytes;
            using (var md5 = MD5.Create())
            {
                bytes = md5.ComputeHash(Encoding.UTF8.GetBytes(value));
            }
            var result = new StringBuilder();
            foreach (byte t in bytes)
            {
                result.Append(t.ToString("X2"));
            }
            return result.ToString();
        }

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