NAudio WaveFileWriter doesn't write file size to wave file

Question

I'm trying to use NAudio to record some sound in C# using WasapiLoopbackCapture and WaveFileWriter.

The problem is that after the recording is finished, the "size" field in the WAV/RIFF header is set to 0, rendering the file unplayable.

I'm using the following code:

    WasapiLoopbackCapture CaptureInstance = null;
    WaveFileWriter RecordedAudioWriter = null;
    void StartSoundRecord()
    {

        string outputFilePath = @"C:\RecordedSound.wav";

        // Redefine the capturer instance with a new instance of the LoopbackCapture class
        CaptureInstance = new WasapiLoopbackCapture();

        // Redefine the audio writer instance with the given configuration
        RecordedAudioWriter = new WaveFileWriter(outputFilePath, CaptureInstance.WaveFormat);
        
        // When the capturer receives audio, start writing the buffer into the mentioned file
        CaptureInstance.DataAvailable += (s, a) =>
        {
            // Write buffer into the file of the writer instance
            RecordedAudioWriter.Write(a.Buffer, 0, a.BytesRecorded);
        };

        // When the Capturer Stops, dispose instances of the capturer and writer
        CaptureInstance.RecordingStopped += (s, a) =>
        {
            RecordedAudioWriter.Dispose();
            RecordedAudioWriter = null;
            CaptureInstance.Dispose();
        };

        // Start audio recording !
        CaptureInstance.StartRecording();

    }

    void StopSoundRecord()
    {
        if(CaptureInstance != null)
        {
            CaptureInstance.StopRecording();
        }
    }

(Borrowed from: https://ourcodeworld.com/articles/read/702/how-to-record-the-audio-from-the-sound-card-system-audio-with-c-using-naudio-in-winforms )

Which I'm testing with simply:

    StartSoundRecord();
    Thread.Sleep(10000);
    StopSoundRecord();

What am I missing, why isn't WaveFileWriter writing the size field? I have tried also calling the Flush() and Close() methods before disposing. But it makes no difference.

Sure, I could write a method to find out the size of the file and manually writing it to the final file, but that seems unnecessary.

Answer 1

Found the solution.

Calling RecordedAudioWriter.Flush() after every Write made it work just fine.

Don't know if doing so might be inefficient (as I assume flush is blocking until data is written to disk), but for my application that is not an issue.