public class MessageSender
    {
        private readonly string _appKey;
        private readonly string _appSecret;
        private readonly string _serverUrl;

        public MessageSender(string url, string appKey, string appSecret)
        {
            _serverUrl = url;
            _appKey = appKey;
            _appSecret = appSecret;
        }

        public string SmsType { get; set; } = "normal";
        public string SmsFreeSignName { get; set; } = "生日提醒";
        public string SmsParam { get; set; }
        public string RecNum { get; set; }
        public string SmsTemplateCode { get; set; } = "SMS_24695114";

        public string GetApiName()
        {
            return "alibaba.aliqin.fc.sms.num.send";
        }

        public string SendMessage()
        {
            HttpClient httpClient = new HttpClient();

            httpClient.DefaultRequestHeaders.Add("Accept-Encoding", "gzip");
            //httpClient.DefaultRequestHeaders.Add("KeepAlive", "true");
            httpClient.DefaultRequestHeaders.Add("user-agent", "top-sdk-net");
            httpClient.DefaultRequestHeaders.Add("Method", "Post");
            httpClient.DefaultRequestHeaders.Add("Accept", "text/xml,text/javascript");
            httpClient.DefaultRequestHeaders.Add("Host", "gw.api.taobao.com");
            httpClient.Timeout = new TimeSpan(0, 0, 100);

            byte[] postData =http://www.mamicode.com/ GetPostData();

            HttpRequestMessage request = new HttpRequestMessage(HttpMethod.Post, _serverUrl);
            request.Headers.Add("Accept-Encoding", "gzip");
            request.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue("application/x-www-form-urlencoded"));
            request.Headers.AcceptCharset.Add(new StringWithQualityHeaderValue("utf-8"));
            request.Content = new StreamContent(new MemoryStream(postData));
            request.Content.Headers.ContentType = new MediaTypeWithQualityHeaderValue("application/x-www-form-urlencoded");

            HttpResponseMessage httpResponseMessage = httpClient.SendAsync(request).GetAwaiter().GetResult();
            string result = httpResponseMessage.Content.ReadAsStringAsync().GetAwaiter().GetResult();

            return result;
        }

        public byte[] GetPostData()
        {
            Dictionary<string, string> dictionary = new Dictionary<string, string>();

            dictionary.Add("rec_num", RecNum);
            dictionary.Add("sms_free_sign_name", SmsFreeSignName);
            dictionary.Add("sms_param", SmsParam);
            dictionary.Add("sms_template_code", SmsTemplateCode);
            dictionary.Add("sms_type", SmsType);
            dictionary.Add("method", "alibaba.aliqin.fc.sms.num.send");
            dictionary.Add("v", "2.0");
            dictionary.Add("sign_method", "hmac");
            dictionary.Add("app_key", _appKey);
            dictionary.Add("format", "xml");
            dictionary.Add("partner_id", "top-sdk-net-20160607");
            dictionary.Add("timestamp", DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss"));
            //dictionary.Add("target_app_key", null);
            //dictionary.Add("session", null);
            dictionary.Add("sign", SignTopRequest(dictionary, null, _appSecret, "hmac"));

            byte[] postData =http://www.mamicode.com/ Encoding.UTF8.GetBytes(BuildQuery(dictionary));

            return postData;
        }

        public string SignTopRequest(IDictionary<string, string> parameters, string body, string secret, string signMethod)
        {
            // 第一步：把字典按Key的字母顺序排序
            IDictionary<string, string> sortedParams = new SortedDictionary<string, string>(parameters, StringComparer.Ordinal);

            // 第二步：把所有参数名和参数值串在一起
            StringBuilder query = new StringBuilder();
            if ("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);
                }
            }

            // 第三步：把请求主体拼接在参数后面
            if (!string.IsNullOrEmpty(body))
            {
                query.Append(body);
            }

            // 第四步：使用MD5/HMAC加密
            byte[] bytes;
            if ("hmac".Equals(signMethod))
            {
                HMACMD5 hmac = new HMACMD5(Encoding.UTF8.GetBytes(secret));
                bytes = hmac.ComputeHash(Encoding.UTF8.GetBytes(query.ToString()));
            }
            else
            {
                query.Append(secret);
                MD5 md5 = MD5.Create();
                bytes = md5.ComputeHash(Encoding.UTF8.GetBytes(query.ToString()));
            }

            // 第五步：把二进制转化为大写的十六进制
            StringBuilder result = new StringBuilder();
            foreach (byte t in bytes)
            {
                result.Append(t.ToString("X2"));
            }

            return result.ToString();
        }

        public string BuildQuery(IDictionary<string, string> parameters)
        {
            if (parameters == null || parameters.Count == 0)
            {
                return null;
            }

            StringBuilder query = new StringBuilder();
            bool hasParam = false;

            foreach (KeyValuePair<string, string> kv in parameters)
            {
                string name = kv.Key;
                string value =http://www.mamicode.com/ kv.Value;
                // 忽略参数名或参数值为空的参数
                if (!string.IsNullOrEmpty(name) && !string.IsNullOrEmpty(value))
                {
                    if (hasParam)
                    {
                        query.Append("&");
                    }

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

            return query.ToString();
        }
    }