流式写入和读取

我正在寻找使此代码线程安全的解决方案：

private Stream ms = new MemoryStream();
public void PlayMp3FromUrl(string url)
{
    new Thread(delegate(object o)
    {
        var response = WebRequest.Create(url).GetResponse();
        using (var stream = response.GetResponseStream())
        {
            byte[] buffer = new byte[65536]; // 64KB chunks
            int read;
            while ((read = stream.Read(buffer, 0, buffer.Length)) > 0)
            {
                var pos = ms.Position;
                ms.Position = ms.Length;
                ms.Write(buffer, 0, read);
                ms.Position = pos;
            }
        }
    }).Start();
    // Pre-buffering some data to allow NAudio to start playing
    while (ms.Length < 65536*10)
        Thread.Sleep(1000);
    ms.Position = 0;
    using (WaveStream blockAlignedStream = new BlockAlignReductionStream(WaveFormatConversionStream.CreatePcmStream(new Mp3FileReader(ms))))
    {
        using (WaveOut waveOut = new WaveOut(WaveCallbackInfo.FunctionCallback()))
        {
            waveOut.Init(blockAlignedStream);
            waveOut.Play();
            while (waveOut.PlaybackState == PlaybackState.Playing)
            {
                System.Threading.Thread.Sleep(100);
            }
        }
    }
}

当您同时使用NAudio播放时，不能将ms.Position更改为ms.Write，是吗？有什么解决方案可以确保线程安全？

还有如果流是无穷的或者很大，如何清除已经播放的流部分？