C#怎么实现手机短信发送功能

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Net;
using System.Text;
using System.Web;
namespace Y_PostSms
{
  public class YMethod
  {
    private string THE_UID = ""; //用户名
    private string THE_KEY = ""; //接口秘钥
    /// <summary>返回UTF-8编码发送接口地址</summary>
    /// <param name="receivePhoneNumber">目的手机号码（多个手机号请用半角逗号隔开）</param>
    /// <param name="receiveSms">短信内容，最多支持400个字，普通短信70个字/条，长短信64个字/条计费</param>
    /// <returns></returns>
    public string GetPostUrl(string smsMob, string smsText)
    {
      string postUrl = "http://utf8.sms.webchinese.cn/?Uid=" + THE_UID + "&key=" + THE_KEY + "&smsMob=" + smsMob + "&smsText=" + smsText;
      return postUrl;
    }
    /// <summary> 发送短信，得到返回值</summary>
    public string PostSmsInfo(string url)
    {
      //调用时只需要把拼成的URL传给该函数即可。判断返回值即可
      string strRet = null;
      if (url == null || url.Trim().ToString() == "")
      {
        return strRet;
      }
      string targeturl = url.Trim().ToString();
      try
      {
        HttpWebRequest hr = (HttpWebRequest)WebRequest.Create(targeturl);
        hr.UserAgent = "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1)";
        hr.Method = "GET";
        hr.Timeout = 30 * 60 * 1000;
        WebResponse hs = hr.GetResponse();
        Stream sr = hs.GetResponseStream();
        StreamReader ser = new StreamReader(sr, Encoding.Default);
        strRet = ser.ReadToEnd();
      }
      catch (Exception ex)
      {
        strRet = null;
      }
      return strRet;
    }
    /// <summary>确认返回信息 </summary>
    public string GetResult(string strRet)
    {
      int result = 0;
      try
      {
        result = int.Parse(strRet);
        switch (result)
        {
          case -1:
            strRet = "没有该用户账户";
            break;
          case -2:
            strRet = "接口密钥不正确,不是账户登陆密码";
            break;
          case -21:
            strRet = "MD5接口密钥加密不正确";
            break;
          case -3:
            strRet = "短信数量不足";
            break;
          case -11:
            strRet = "该用户被禁用";
            break;
          case -14:
            strRet = "短信内容出现非法字符";
            break;
          case -4:
            strRet = "手机号格式不正确";
            break;
          case -41:
            strRet = "手机号码为空";
            break;
          case -42:
            strRet = "短信内容为空";
            break;
          case -51:
            strRet = "短信签名格式不正确,接口签名格式为：【签名内容】";
            break;
          case -6:
            strRet = "IP限制";
            break;
          default:
            strRet = "发送短信数量：" + result;
            break;
        }
      }
      catch (Exception ex)
      {
        strRet = ex.Message;
      }
      return strRet;
    }
  }
}