NAudio: "Unable to instantiate ASIO. Check if STAThread is set"

Question

I'm attempting to route microphone audio into the speakers in NAudio, using ASIO drivers. I have been successful in the NAudio demo project. Copying this code over to a different project (XNA, if relevant) is causing a COMException every time. Here is the method I wrote:

    [STAThread]
    void InitAsio()
    {
        if (this.asioOut != null &&
            (this.asioOut.DriverName != "ASIO4ALL v2" ||
            this.asioOut.ChannelOffset != 0))
        {
            this.asioOut.AudioAvailable -= asioOut_AudioAvailable;
            this.asioOut.Dispose();
            this.asioOut = null;
        }

        // create wave input from mic
        // create device if necessary
        if (this.asioOut == null)
        {
            this.asioOut = new AsioOut();
            BufferedWaveProvider wavprov = new BufferedWaveProvider(new WaveFormat(44100, 1));
            this.asioOut.InputChannelOffset = 0;
            this.asioOut.InitRecordAndPlayback(wavprov, 1, 44100);
            this.asioOut.AudioAvailable += asioOut_AudioAvailable;
        }

        //this.fileName = Path.Combine(Path.GetTempPath(), Guid.NewGuid().ToString() + ".wav");
        //this.writer = new WaveFileWriter(fileName, new WaveFormat(44100, recordChannelCount));
        this.asioOut.Play();
    }

Every time, this method fails in AsioDriver.cs:

    int hresult = CoCreateInstance(ref ASIOGuid, IntPtr.Zero, CLSCTX_INPROC_SERVER, ref ASIOGuid, out pASIOComObject);
    if ( hresult != 0 )
    {
        throw new COMException("Unable to instantiate ASIO. Check if STAThread is set",hresult);
    }

I have no idea what's happening and why. Same code works in the NAudio demo project. Any ideas?

Answer 1

The STAThread attribute can only be applied to the Main method of your application. It won't work on any other method.