create a http server and add a custom header to the response in csharp

main.cs
using System;
using System.Net;

public class HttpServer
{
    private readonly string _url;
    private readonly HttpListener _listener;

    public HttpServer(string url)
    {
        _url = url;
        _listener = new HttpListener();
        _listener.Prefixes.Add(_url);
    }

    public void Start()
    {
        _listener.Start();
        Console.WriteLine($"Server started at {_url}");
        while (true)
        {
            var context = _listener.GetContext();
            var response = context.Response;
            response.AddHeader("Custom-Header", "Custom header value");
            var message = "Hello World!";
            var buffer = System.Text.Encoding.UTF8.GetBytes(message);
            response.ContentLength64 = buffer.Length;
            var output = response.OutputStream;
            output.Write(buffer, 0, buffer.Length);
            output.Close();
        }
    }

    public void Stop()
    {
        _listener.Stop();
        _listener.Close();
    }
}

class Program
{
    static void Main(string[] args)
    {
        var server = new HttpServer("http://localhost:8080/");
        server.Start();
        Console.WriteLine("Press any key to stop the server");
        Console.ReadKey();
        server.Stop();
    }
}
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