using System;
using System.IO;
using System.Net;
using System.Text;

public static class HttpHelper
{
    /// <summary>
    /// 发送 POST 请求（Content-Type: application/json）
    /// </summary>
    public static string HttpPost(string url, string jsonBody)
    {
        var request = (HttpWebRequest)WebRequest.Create(url);
        request.Method = "POST";
        request.ContentType = "application/json;charset=UTF-8";

        byte[] data = Encoding.UTF8.GetBytes(jsonBody);
        request.ContentLength = data.Length;

        // 写入 Body
        using (var stream = request.GetRequestStream())
        {
            stream.Write(data, 0, data.Length);
        }

        // 接收响应
        using (var response = (HttpWebResponse)request.GetResponse())
        {
            using (var reader = new StreamReader(response.GetResponseStream(), Encoding.UTF8))
            {
                return reader.ReadToEnd();
            }
        }
    }
}