C#：HttpWebRequest POST数据不工作

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

public class Program
{
    public static void Main()
    {
        string url = "https://example.com/api";
        string postData = "name=John&age=30";

        HttpWebRequest request = (HttpWebRequest)WebRequest.Create(url);
        request.Method = "POST";
        request.ContentType = "application/x-www-form-urlencoded";
        byte[] data = Encoding.UTF8.GetBytes(postData);
        request.ContentLength = data.Length;

        using (Stream stream = request.GetRequestStream())
        {
            stream.Write(data, 0, data.Length);
        }

        using (HttpWebResponse response = (HttpWebResponse)request.GetResponse())
        {
            using (Stream responseStream = response.GetResponseStream())
            {
                using (StreamReader reader = new StreamReader(responseStream))
                {
                    string responseText = reader.ReadToEnd();
                    Console.WriteLine(responseText);
                }
            }
        }
    }
}