C#

using System;
using System.Collections.Generic;
using System.Net.Http;
using System.Security.Cryptography;
using System.Text;
namespace SmsDemo
{
    class SendSms
    {
        private static Object generateSign(string signatureString, string secretKey, bool raw_output = false)
        {
            var enc = Encoding.UTF8;
            HMACSHA1 hmac = new HMACSHA1(enc.GetBytes(secretKey));
            hmac.Initialize();
            byte[] buffer = enc.GetBytes(signatureString);
            if (raw_output)
            {
                return hmac.ComputeHash(buffer);
            }
            else
            {
                return BitConverter.ToString(hmac.ComputeHash(buffer)).Replace("-", "").ToLower();
            }
        }
        public static void send()
        {
            String url = "https://api.yisu.com/sms/sendSms";
            String accessId = "*****";
            String accessSecret = "*****";
            Random rnd = new Random();
            TimeSpan ts = DateTime.UtcNow - new DateTime(1970, 1, 1, 0, 0, 0, 0);
            List<KeyValuePair<String, String>> paramList = new List<KeyValuePair<String, String>>();
            paramList.Add(new KeyValuePair<String, String>("accessId", accessId));
            paramList.Add(new KeyValuePair<String, String>("templateCode", "100001"));
            paramList.Add(new KeyValuePair<String, String>("phone", "13800000000"));
            paramList.Add(new KeyValuePair<String, String>("timestamp", Convert.ToInt64(ts.TotalSeconds).ToString()));
            paramList.Add(new KeyValuePair<String, String>("nonce", rnd.Next(1, 1000000).ToString()));
            paramList.Add(new KeyValuePair<String, String>("templateVars", "{\"code\":\"123456\",\"min\":\"5\"}"));
            paramList.Sort(
                delegate (KeyValuePair<String, String> p1, KeyValuePair<String, String> p2)
                {
                    return p1.Key.CompareTo(p2.Key);
                }
            );
            var param_str = "";
            foreach (var param in paramList)
            {
                param_str += param.Key.ToString() + "=" + param.Value.ToString() + "&";
            }
            param_str = param_str.Substring(0, param_str.Length - 1);
            byte[] sign = (byte[])generateSign(param_str, accessSecret, true);
            paramList.Add(new KeyValuePair<String, String>("signature", Convert.ToBase64String(sign)));
            HttpClient client = null;
            HttpResponseMessage response = null;
            try
            {
                client = new HttpClient();
                response = client.PostAsync(url, new FormUrlEncodedContent(paramList)).Result;
                String result = response.Content.ReadAsStringAsync().Result;
                Console.WriteLine("result:{0}", result);
            }
            catch (Exception e)
            {
                Console.WriteLine("\nException Caught!");
                Console.WriteLine("Message :{0} ", e.Message);
            }
            finally
            {
                if (null != response)
                {
                    response.Dispose();
                }
                if (null != client)
                {
                    client.Dispose();
                }
            }
        }
        static void Main(string[] args)
        {
            send();
        }
    }
}