C＃：NAudio-空路径名不合法

Question

I've posted about this before detailing error messages, highlighting where the exception is being thrown, people seem to be ignoring what I write and just dive into the code making guesses.

So I'm going to post the code and while I admit I don't know EXACTLY what is wrong, I know where so I'd appreciate it if you could indulge my newbieness.

WaveIn sourceStream = null;
    WaveFileWriter waveWriter = null;
    SaveFileDialog save = new SaveFileDialog();

 private void sourceStream_DataAvailable(object sender, WaveInEventArgs e)
    {
        if (waveWriter == null) return;
        //Adds bytes to the wave file, storing them in a buffer? 
        waveWriter.Write(e.Buffer, 0, e.BytesRecorded);
        waveWriter.Flush();
    }

    private void recordButton_Click(object sender, RoutedEventArgs e)
    {

        MainWindow mw = new MainWindow();
        //Get device number from MainWindow.DeviceButton().
        int devNum = mw.DeviceButton();

        if (recordButton.Content.ToString() == "RECORD")
        {
            recordButton.Content = "STOP";
            //Start recording audio. 
            sourceStream = new WaveIn();

            sourceStream.DeviceNumber = devNum;

            //1. Set the sample rate(?). 2. Get number of channels supported on the device.
            sourceStream.WaveFormat = new WaveFormat(44100, WaveIn.GetCapabilities(devNum).Channels);


            waveWriter = new WaveFileWriter(save.FileName, sourceStream.WaveFormat);

            sourceStream.DataAvailable += new EventHandler<WaveInEventArgs>(sourceStream_DataAvailable);
            sourceStream.StartRecording();
        }
        else if(recordButton.Content.ToString() == "STOP")
        {

            sourceStream.StopRecording();
            waveWriter.Dispose();
            save.Filter = "Wave Files (*.wav)|*.wav;";
                if (save.ShowDialog() != true) return;



            recordButton.Content = "RECORD";



        }
    }

The error is on this line:

waveWriter = new WaveFileWriter(save.FileName, sourceStream.WaveFormat);

It is a runtime error, triggering a System.ArgumentException. Very general, the only useful thing I get is that 'Empty path name is not legal' message.

Now, I'm following along with some example code in order to familiarize myself with NAudio and they don't ever actually set save.FileName(). So naturally I didn't, honestly I don't think it's necessary or the problem, but thought it worth mentioning just in case.

Personally, and I don't see this in the sample code either, I don't see the connection between the save dialogue and actually saving my audio stream. Perhaps I'm missing this component?

Answer 1

I see the call to:

SaveFileDialog save = new SaveFileDialog();

However, I do not see where you call

save.ShowDialog()

before you reference the file name. You will need to make that call in order to select the path/filename. You should then check to see if the FileName is empty before calling a method that references it. For example,

if (!string.IsNullOrEmpty(save.FileName)) 
{
    <Code Goes Here>
}