C# Naudio StreamMixToDisk错误

我在键入wav文件名并让nAudio将其接受为StreamMixToDisk时遇到问题

Public Sub SetupAudio()
    'Setup the Mixer
    mixer = New WaveMixerStream32()
    mixer.AutoStop = False

    If waveOutDevice Is Nothing Then
        'waveOutDevice = new AsioOut();

        waveOutDevice = New WaveOut(0, 300, False)

        waveOutDevice.Init(mixer)
        waveOutDevice.Play()
    End If
End Sub

Private Sub cmbRecordDirect_Click(sender As Object, e As EventArgs) Handles cmbRecord.Click
    Dim saveFileDialog As New SaveFileDialog()
    saveFileDialog.Title = "Select output file:"
    saveFileDialog.Filter = "WAV Files (*.wav)|*.wav"
    saveFileDialog.FileName = outputFilename

    If saveFileDialog.ShowDialog() = DialogResult.OK Then
        outputFilename = saveFileDialog.FileName
        mixer.StreamMixToDisk(outputFilename)
        mixer.StartStreamingToDisk()
        cmbRecordDirect.Enabled = False
        cmbStopDirect.Enabled = True
        cmbPauseDirect.Enabled = True
    End If
End Sub

outputFilename是c:\test.wav，但一旦它到达混音器.StreamMixToDisk（outputFilename）它就会出现一个错误，显示：

A first chance exception of type 'System.NullReferenceException'
Object reference not set to an instance of an object.

上面转换为VB.net的C#代码如下：

private void cmbRecordDirect_Click(object sender, EventArgs e)
    {
        SaveFileDialog saveFileDialog = new SaveFileDialog();
        saveFileDialog.Title = "Select output file:";
        saveFileDialog.Filter = "WAV Files (*.wav)|*.wav";
        saveFileDialog.FileName = outputFilename;
        if (saveFileDialog.ShowDialog() == DialogResult.OK)
        {
            outputFilename = saveFileDialog.FileName;
            mixer.StreamMixToDisk(outputFilename);
            mixer.StartStreamingToDisk();
            cmbRecordDirect.Enabled = false;
            cmbStopDirect.Enabled = true;
            cmbPauseDirect.Enabled = true;
        }
    }

---

发生此错误的原因是什么？

我没有调用SetupAudio（）来启动混音器

的形式，似乎

混音器在任何地方都没有实例化，因此为空。如果
mixer
本身不为null，则
StreamMixToDisk
方法中的对象为空。
Public Sub SetupAudio()
    'Setup the Mixer
    mixer = New WaveMixerStream32()
    mixer.AutoStop = False

    If waveOutDevice Is Nothing Then
        'waveOutDevice = new AsioOut();

        waveOutDevice = New WaveOut(0, 300, False)

        waveOutDevice.Init(mixer)
        waveOutDevice.Play()
    End If
End Sub

Private Sub cmbRecordDirect_Click(sender As Object, e As EventArgs) Handles cmbRecord.Click
    Dim saveFileDialog As New SaveFileDialog()
    saveFileDialog.Title = "Select output file:"
    saveFileDialog.Filter = "WAV Files (*.wav)|*.wav"
    saveFileDialog.FileName = outputFilename

    If saveFileDialog.ShowDialog() = DialogResult.OK Then
        outputFilename = saveFileDialog.FileName
        mixer.StreamMixToDisk(outputFilename)
        mixer.StartStreamingToDisk()
        cmbRecordDirect.Enabled = False
        cmbStopDirect.Enabled = True
        cmbPauseDirect.Enabled = True
    End If
End Sub