Step 1: Download Audio Capture Pro SDK ActiveX Installer and installed it.

Step 2: Create win form project, add a buttons into the form.

Step 3: Add following code in buttons click event. Assume your first audio device is microphone.

private void button1_Click(object sender, System.EventArgs e)
{
axAudioCapture1.AudioDevice=0;
axAudioCapture1.AudioMixWithSpeaker=true;
axAudioCapture1.AudioMixSelectedSpeaker=0;
axAudioCapture1.AudioFileName="c:\\test.mp3";
axAudioCapture1.MP3AudioBitrate=128;
axAudioCapture1.OutputType=2;
axAudioCapture1.Start();
}