struct MixerCaps

   Private Structure MixerCaps

   private static extern uint MixerGetDevCaps(int mixerId, ref MixerCaps mixerCaps, int mixerCapsSize);

   Private Shared Function MixerGetDevCaps(ByVal mixerId As Integer, ByRef mixerCaps As MixerCaps, ByVal mixerCapsSize As Integer) As UInteger

MixerCaps is in Structures.MIXERCAPS

       private static extern uint MixerGetDevCaps(int mixerId, ref MixerCaps mixerCaps, int mixerCapsSize);

       struct MixerCaps

           MixerCaps caps = new MixerCaps();