使用`System.Net.WebClient`類發送HTTP請求來調用阿里雲短信API

using System;
using System.Collections.Specialized;
using System.Net;

class Program
{
    static void Main(string[] args)
    {
        string accessKeyId = "<your-access-key-id>";
        string accessKeySecret = "<your-access-key-secret>";
        string phoneNumber = "<target-phone-number>";
        string signName = "<your-signature>";
        string templateCode = "<your-template-code>";
        string templateParam = "{\"code\":\"123456\"}";

        using (WebClient client = new WebClient())
        {
            NameValueCollection values = new NameValueCollection();
            values.Add("AccessKeyId", accessKeyId);
            values.Add("Action", "SendSms");
            values.Add("Format", "JSON");
            values.Add("PhoneNumbers", phoneNumber);
            values.Add("RegionId", "cn-hangzhou");
            values.Add("SignName", signName);
            values.Add("SignatureMethod", "HMAC-SHA1");
            values.Add("SignatureNonce", Guid.NewGuid().ToString());
            values.Add("SignatureVersion", "1.0");
            values.Add("TemplateCode", templateCode);
            values.Add("TemplateParam", templateParam);
            values.Add("Timestamp", DateTime.UtcNow.ToString("yyyy-MM-ddTHH:mm:ssZ"));
            values.Add("Version", "2017-05-25");

            string sortedQueryString = GetSortedQueryString(values);
            string stringToSign = "GET&%2F&" + Uri.EscapeDataString(sortedQueryString);
            string signature = ComputeSignature(stringToSign, accessKeySecret + "&");

            string url = "http://dysmsapi.aliyuncs.com/?" + sortedQueryString + "&Signature=" + Uri.EscapeDataString(signature);
            string response = client.DownloadString(url);

            Console.WriteLine("SMS sent, response: " + response);
        }
    }

    static string GetSortedQueryString(NameValueCollection values)
    {
        var sortedValues = values.AllKeys.Select(key => key + "=" + Uri.EscapeDataString(values[key]));
        return string.Join("&", sortedValues.OrderBy(s => s));
    }

    static string ComputeSignature(string stringToSign, string accessKeySecret)
    {
        using (var hmac = new System.Security.Cryptography.HMACSHA1(Encoding.UTF8.GetBytes(accessKeySecret)))
        {
            var hashBytes = hmac.ComputeHash(Encoding.UTF8.GetBytes(stringToSign));
            return Convert.ToBase64String(hashBytes);
        }
    }
}