struct MIDIOUTCAPS

    // values for wTechnology field of MIDIOUTCAPS structure

    // flags for dwSupport field of MIDIOUTCAPS structure

MidiOutCaps outCaps = new MidiOutCaps();

public static extern MMRESULT midiOutGetDevCaps(UIntPtr uDeviceID, ref MIDIOUTCAPS lpMidiOutCaps, uint cbMidiOutCaps);

MIDIOUTCAPS

Use (uint)Marshal.SizeOf(typeof(MIDIOUTCAPS)) for cbMidiOutCaps.

    struct MIDIOUTCAPS

        MIDIOUTCAPS caps = new MIDIOUTCAPS();

        midiOutGetDevCaps((UIntPtr) x, out caps, (uint)Marshal.SizeOf(typeof(MIDIOUTCAPS)));