New Post: 'Mic' plug versus 'Line In' plug

I cannot record by my 'Line-In' plug? I use Win 7 and this setup for my record-button:

private void button2_Click(object sender, EventArgs e)

    {
        if (SourceList.SelectedItems.Count == 0) return;

        int deviceNumber = SourceList.SelectedItems[0].Index;

        sourceStream = new NAudio.Wave.WaveIn();
        sourceStream.DeviceNumber = deviceNumber;
        sourceStream.WaveFormat = new NAudio.Wave.WaveFormat(44100, NAudio.Wave.WaveIn.GetCapabilities(deviceNumber).Channels);

        NAudio.Wave.WaveInProvider waveIn = new NAudio.Wave.WaveInProvider(sourceStream);

        waveOut = new NAudio.Wave.DirectSoundOut();
        waveOut.Init(waveIn);

        sourceStream.StartRecording();
        waveOut.Play();
    }

The setup has no trouble in recording while I am using the 'Microphone' plug???

For extra info I use a little mixer, that collects the audio from 4 small contact-surface microphones, and thereafter sends a signal that cannot be recieved by my 'Microphone' plug - still the Naudio should be able to recieve by the 'Line In' plug instead (one should think)

(As a side remark I have the old audio editing software of Cool Edit on my PC, that doesn't differ between the plugs and records effortsly by both plugs)