static void Main(string[] args)
        {
            string l_strUrl = "http://www.baidu.com";  // 请求URL1
            HttpWebRequest l_httpWebRequest = (HttpWebRequest)HttpWebRequest.Create(l_strUrl);  // 创建连接
            l_httpWebRequest.Method = "get";  // 请求方式
            l_httpWebRequest.Timeout = 10000;  // 超时时间
            var request = l_httpWebRequest.GetResponse();  // 获取响应
            StreamReader l_streamR = new StreamReader(request.GetResponseStream(), Encoding.UTF8);  // 转换为流
            string l_strXml = l_streamR.ReadToEnd();  // 获取流中的数据
            l_streamR.Close();  // 关闭
            File.WriteAllText("D:/Code/Demo/Demo/upload/index.html", l_strXml);  // 将获取到的信息写入文本
            //
            //Console.Write(l_strXml);


            Console.ReadKey();
        }

SeDemo.cs：
using SeDemo.Entitys;
using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Net;
using System.Net.Http;
using System.Text;
using System.Web;
using System.Web.Http;

namespace SeDemo.Controllers
{
    public class DefaultController : ApiController
    {
        [HttpGet]
        public string Get()
        {
            HttpWebRequest l_httpWebRequest = (HttpWebRequest)HttpWebRequest.Create("http://localhost:61614/api/Index");
            l_httpWebRequest.Method = "POST";
            l_httpWebRequest.ContentType = "application/json";
            l_httpWebRequest.Timeout = 100000;

            // 构造相应数据
            string l_data = "{id:1,name:‘namejr‘,age:12}";  // 值得注意的是，这里的构造数据和前段的一样
            byte[] l_byteData = Encoding.UTF8.GetBytes(l_data.ToString());
            l_httpWebRequest.ContentLength = l_byteData.Length;
            l_httpWebRequest.GetRequestStream().Write(l_byteData, 0, l_byteData.Length);
            //Stream l_stream = l_httpWebRequest.GetRequestStream();
            //l_stream.Write(l_byteData, 0, l_byteData.Length);
            //l_stream.Close();

            // 获取响应并解析
            var l_response = l_httpWebRequest.GetResponse();
            StreamReader l_sr = new StreamReader(l_response.GetResponseStream(), Encoding.UTF8);
            string l_retXml = l_sr.ReadToEnd();
            l_sr.Close();
            return l_retXml;
        }
    }
}
==============================================
using SeDemo.Entitys;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Net;
using System.Net.Http;
using System.Web.Http;

namespace SeDemo.Controllers
{
    public class IndexController : ApiController
    {
        [HttpGet]
        public string Get()
        {
            return "Hello world!!!";
        }

        [HttpPost]
        public string Post([FromBody]MessageInfo a_entitys)
        {
            string l_strTemp = "";
            if(a_entitys!=null&&!string.IsNullOrEmpty(a_entitys.id.ToString()))
            {
                l_strTemp = string.Format("{0}=>{1}=>{2}", a_entitys.id, a_entitys.name, a_entitys.age);
            }
            else
            {
                l_strTemp = string.Format("传不上来哟!!!");
            }
            return l_strTemp;
        }
    }
}