C#使用Http Post方式传递Json数据字符串调用Web Service

[WebMethod]
    public string Project(string paramaters)
    {
      return paramaters;
    }

public string Post(string methodName, string jsonParas)
    {
      string strURL = Url + "/" + methodName;

      //创建一个HTTP请求 
      HttpWebRequest request = (HttpWebRequest)WebRequest.Create(strURL);
      //Post请求方式 
      request.Method = "POST";
      //内容类型
      request.ContentType = "application/x-www-form-urlencoded";

      //设置参数，并进行URL编码 
      //虽然我们需要传递给服务器端的实际参数是JsonParas(格式：[{\"UserID\":\"0206001\",\"UserName\":\"ceshi\"}])，
      //但是需要将该字符串参数构造成键值对的形式（注："paramaters=[{\"UserID\":\"0206001\",\"UserName\":\"ceshi\"}]"），
      //其中键paramaters为WebService接口函数的参数名，值为经过序列化的Json数据字符串
      //最后将字符串参数进行Url编码
      string paraUrlCoded = System.Web.HttpUtility.UrlEncode("paramaters");
      paraUrlCoded += "=" + System.Web.HttpUtility.UrlEncode(jsonParas);

      byte[] payload;
      //将Json字符串转化为字节 
      payload = System.Text.Encoding.UTF8.GetBytes(paraUrlCoded);
      //设置请求的ContentLength  
      request.ContentLength = payload.Length;
      //发送请求，获得请求流 

      Stream writer;
      try
      {
        writer = request.GetRequestStream();//获取用于写入请求数据的Stream对象
      }
      catch (Exception)
      {
        writer = null;
        Console.Write("连接服务器失败!");
      }
      //将请求参数写入流
      writer.Write(payload, 0, payload.Length);
      writer.Close();//关闭请求流

      String strValue = "";//strValue为http响应所返回的字符流
      HttpWebResponse response;
      try
      {
        //获得响应流
        response = (HttpWebResponse)request.GetResponse();
      }
      catch (WebException ex)
      {
        response = ex.Response as HttpWebResponse;
      }

      Stream s = response.GetResponseStream();

      //服务器端返回的是一个XML格式的字符串，XML的Content才是我们所需要的Json数据
      XmlTextReader Reader = new XmlTextReader(s);
      Reader.MoveToContent();
      strValue = Reader.ReadInnerXml();//取出Content中的Json数据
      Reader.Close();
      s.Close();

      return strValue;//返回Json数据
    }