Post Json数据到url接口

using System;
using System.Windows.Forms;

namespace api测试程序
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }
        private void Form1_Load(object sender, EventArgs e)
        {

        }

        private void btn_postJson_Click(object sender, EventArgs e)
        {
            string url = tb_url.Text;

            var request = (System.Net.HttpWebRequest)System.Net.WebRequest.Create(url);    //创建了一个http请求
            request.ContentType = "application/json;charset=UTF-8";
            request.Method = "POST";     //请求方式Post

            byte[] payload = System.Text.Encoding.UTF8.GetBytes(tb_json.Text);

            //设置请求的 ContentLength 
            request.ContentLength = payload.Length;
            using (System.IO.Stream streamWriter = request.GetRequestStream())
            {
                streamWriter.Write(payload, 0, payload.Length);
            }

            var response = (System.Net.HttpWebResponse)request.GetResponse();
            using (var streamReader = new System.IO.StreamReader(response.GetResponseStream()))
            {
                var result = streamReader.ReadToEnd();
                tb_reply.Text = result;
            }
        }
    }
}