FastList.IndexOf C# (CSharp) Method

    public int IndexOf(T item) {
        if (size <= 0 || array == null) { return -1;}
        for (int i = 0; i < size; i++) {
            if (item.Equals(array[i])) { return i;}
        }
        return -1;
    }

 private static int TrackVoiceStats(MidiEvent midiEvent, FastList <byte> instList, FastList <byte> drumList, FastList <byte> channelList, int noteOnCount)
 {
     if (midiEvent.Command == MidiEventTypeEnum.NoteOn)
     {
         var chan = midiEvent.Channel;
         if (channelList.IndexOf((byte)chan) == -1)
         {
             channelList.Add((byte)chan);
         }
         noteOnCount++;
     }
     else if (midiEvent.Command == MidiEventTypeEnum.ProgramChange)
     {
         var chan = midiEvent.Channel;
         var prog = midiEvent.Data1;
         if (chan == MidiHelper.DrumChannel)
         {
             if (drumList.IndexOf((byte)prog) == -1)
             {
                 drumList.Add((byte)prog);
             }
         }
         else
         {
             if (instList.IndexOf((byte)prog) == -1)
             {
                 instList.Add((byte)prog);
             }
         }
     }
     return(noteOnCount);
 }