private WasapiCapture capture;
    private WaveWriter writer;

        private void startRecording()
    {
        capture = new WasapiCapture();
        capture.Initialize();
        writer = new WaveWriter("file.wav", capture.WaveFormat);
        capture.DataAvailable += (s, capData) =>
        {
            writer.Write(capData.Data, capData.Offset, capData.ByteCount);
        };
        capture.Start();
    }

    private void stopRecording()
    {
        if (writer != null && capture != null)
        {
            capture.Stop();
            writer.Dispose();
            capture.Dispose();
        }
    }