MIDIINPROC Delegate

public delegate void MIDIINPROC(
	IntPtr handle,
	MIDIMessage msg,
	IntPtr instance,
	IntPtr param1,
	IntPtr param2
)

Public Delegate Sub MIDIINPROC ( 
	handle As IntPtr,
	msg As MIDIMessage,
	instance As IntPtr,
	param1 As IntPtr,
	param2 As IntPtr
)

private MIDIINPROC _midiProc;
private IntPtr _midiInHandle;
...
// Open the Midi device #2
_midiProc = new MIDIINPROC(MyMidiProc);
MIDIError ret = Midi.MIDI_InOpen(ref _midiInHandle, 2, _midiProc, IntPtr.Zero, MIDIFlags.MIDI_IO_STATUS);
if (ret == MIDIError.MIDI_OK)
{
  // supply the device with 2 buffers
  AddSysExBuffer(_midiInHandle, 1024);
  AddSysExBuffer(_midiInHandle, 1024);
  // Start the device
  ret = Midi.MIDI_InStart(_midiInHandle);
}
...
// Stop the device
Midi.MIDI_InReset(_midiInHandle);
// when not needed anymore...close the device
Midi.MIDI_InClose(_midiInHandle);
...
// prepare receiving system-exclusive messages
private void AddSysExBuffer(IntPtr handle, int size)
{
  // prepare a empty midi header
  MIDI_HEADER header = new MIDI_HEADER(size);
  header.Prepare(true, handle);
  // If the header was perpared successfully.
  if (header.HeaderPtr != IntPtr.Zero)
  {
    // Add the buffer to the InputDevice.
    Midi.MIDI_InAddBuffer(handle, header.HeaderPtr);
  }
}

public void MyMidiProc(IntPtr handle, MIDIMessage msg, IntPtr instance, IntPtr param1, IntPtr param2)
{
  // handle all Midi messages here
  if (msg == MIDIMessage.MIM_OPEN)
  {
    // nothing to do
  }
  else if (msg == MIDIMessage.MIM_CLOSE)
  {
    // handle is from now on invalid
  }
  else if (msg == MIDIMessage.MIM_DATA)
  {
    // process the message...
    int p1 = param1.ToInt32();
    int p2 = param2.ToInt32();
    ...
    // or
    MidiShortMessage shortMsg = new MidiShortMessage(param1, param2);
    ...
  }
  else if (msg == MIDIMessage.MIM_MOREDATA)
  {
    // we are not fast enough in this callback to keep up
    // the input device is sending messages to fast
    ...
  }
  else if (msg == MIDIMessage.MIM_LONGDATA)
  {
    // process the message...
    // param1 will contain the pointer to the MIDI_HEADER
    MIDI_HEADER header = MIDI_HEADER(param1);
    byte[] data = header.Data;
    ...
    header.Unprepare(true, handle);
    // add a new buffer
    // since we should constantly provide new buffers until we finished recording
    AddSysExBuffer(handle, 1024);
  }
  else if (msg == MIDIMessage.MIM_ERROR)
  {
    // process the invalid message...
    MidiShortMessage errorMsg = new MidiShortMessage(param1, param2);
    ...
  }
  else if (msg == MIDIMessage.MIM_LONGERROR)
  {
    // process the invalid message...
    // param1 will contain the pointer to the MIDI_HEADER
    MidiSysExMessage errorSysExMsg = new MidiSysExMessage(true, handle, param1);
    ...
    // add a new buffer
    // since we should constantly provide new buffers until we finished recording
    AddSysExBuffer(handle, 1024);
  }
}

Private _midiProc As MIDIINPROC
Private _midiInHandle As IntPtr
...
' Open the Midi device #2
_midiProc = New MIDIINPROC(AddressOf MyMidiProc)
Dim ret As MIDIError = Midi.MIDI_InOpen(_midiInHandle, 2, _midiProc, IntPtr.Zero, MIDIFlags.MIDI_IO_STATUS)
If ret = MIDIError.MIDI_OK Then
  ' supply the device with 2 buffers
  AddSysExBuffer(_midiInHandle, 1024)
  AddSysExBuffer(_midiInHandle, 1024)
  ' Start the device
  ret = Midi.MIDI_InStart(_midiInHandle)
End If
...
' Stop the device
Midi.MIDI_InReset(_midiInHandle)
' when not needed anymore...close the device
Midi.MIDI_InClose(_midiInHandle)
...
' prepare receiving system-exclusive messages
Private Sub AddSysExBuffer(handle As IntPtr, size As Integer)
  ' prepare a empty midi header
  Dim header As New MIDI_HEADER(size)
  header.Prepare(True, handle)
  ' If the header was perpared successfully.
  If header.HeaderPtr <> IntPtr.Zero Then
    ' Add the buffer to the InputDevice.
    Midi.MIDI_InAddBuffer(handle, header.HeaderPtr)
  End If
End Sub

Public Sub MyMidiProc(handle As IntPtr, msg As MIDIMessage, instance As IntPtr, param1 As IntPtr, param2 As IntPtr)
  ' handle all Midi messages here
  If msg = MIDIMessage.MIM_OPEN Then
    ' nothing to do
  Else
    If msg = MIDIMessage.MIM_CLOSE Then
      ' handle is from now on invalid
    Else
      If msg = MIDIMessage.MIM_DATA Then
        ' process the message...
        Dim p1 As Integer = param1.ToInt32()
        Dim p2 As Integer = param2.ToInt32()
        ...
        ' or
        Dim shortMsg As New MidiShortMessage(param1, param2)
        ...
      Else
        If msg = MIDIMessage.MIM_MOREDATA Then
          ' we are not fast enough in this callback to keep up
          ' the input device is sending messages to fast
          ...
        Else
          If msg = MIDIMessage.MIM_LONGDATA Then
            ' process the message...
            ' param1 will contain the pointer to the MIDI_HEADER
            Dim header As MIDI_HEADER = MIDI_HEADER(param1)
            Dim data As Byte() = header.Data
            ...
            header.Unprepare(True, handle)
            ' add a new buffer
            ' since we should constantly provide new buffers until we finished recording
            AddSysExBuffer(handle, 1024)
          Else
            If msg = MIDIMessage.MIM_ERROR Then
              ' process the invalid message...
              Dim errorMsg As New MidiShortMessage(param1, param2)
              ...
            Else
              If msg = MIDIMessage.MIM_LONGERROR Then
                ' process the invalid message...
                ' param1 will contain the pointer to the MIDI_HEADER
                Dim errorSysExMsg As New MidiSysExMessage(True, handle, param1)
                ...
                ' add a new buffer
                ' since we should constantly provide new buffers until we finished recording
                AddSysExBuffer(handle, 1024)
              End If
            End If
          End If
        End If
      End If
    End If
  End If
End Sub