HttpListener异步上下文泄漏

我有一个简单的HTTPServer实现，它使用System.Net.HttpListener。似乎我的AsyncCallbacks没有以某种方式处理，因此导致泄漏。

public abstract class HttpServer : IHttpServer, IDisposable
{
    protected readonly HttpListener HttpListener = new HttpListener();
    protected HttpServer(IEnumerable<string> prefixes)
    {
        WaitOnStartup = new AutoResetEvent(false);
        foreach (var prefix in prefixes)
        {
            HttpListener.Prefixes.Add(prefix);
        }
    }
    private void Process()
    {
        var result = HttpListener.BeginGetContext(ContextReceived, HttpListener);
        result.AsyncWaitHandle.WaitOne(30000);
        result.AsyncWaitHandle.Dispose();
    }
    protected abstract void ContextReceived(IAsyncResult ar);
    [...]
}
public class MyHttpServer : HttpServer
{
    public MyHttpServer(IEnumerable<string> prefixes) : base(prefixes) { }
    protected override void ContextReceived(IAsyncResult ar)
    {
        var listener = ar.AsyncState as HttpListener;
        if (listener == null) return;
        var context = listener.EndGetContext(ar);
        try
        {
            var request = context.Request;
            var response = context.Response;
            //handle the request...
        }
        finally
        {
            context.Response.Close();
            listener.Close();
        }
    }
}

如果我运行内存分析器，它看起来像async句柄(BeginGetContext)不处置，这意味着AsyncCallback对象不断增加....

我错过了什么?

更新时间:下面是基类(HttpServer)的dispose ()

protected virtual void Dispose(bool disposing)
{
    if (_disposed)
        return;
    if (disposing)
    {
        // Free any other managed objects here. 
        HttpListener.Stop();
        HttpListener.Close();
        WaitOnStartup.Dispose();
    }
    // Free any unmanaged objects here. 
    //
    _disposed = true;
}