How do you turn subtitles on and off while the video is playing in LibVLCSharp?

I can set it when I initialize the media player. Once the media player is playing the video, how can I toggle the subtitles on and off during playback?

I've tried options here but can't get it to work.

https://wiki.videolan.org/VLC_command-line_help/

Thanks in advance

UPDATE:

I got the subtitles to turn off and on before play with

public void PlayMedia(string mediaFileName)
    {
        _media = new Media(_libVLC, new Uri(mediaFileName));
        _media.AddOption(string.Format(@":sub-track-id={0}", int.MaxValue)); //turn off
        _mp.Play(_media);
    }

While playing I tried to do something like

_media.AddOption(string.Format(@":sub-track-id={0}", 2)); //2 was value in SpuDescription in debugger to enable subtitles

Referenced: https://github.com/Stremio/react-native-vlc2/pull/4/commits/e5646acab6423ceb328c31eaeac3200d6ba0b91f

This does not work while the media player is playing

How do I changed this value while media is playing?

UPDATE 2

I found an UGLY workaround (see below) but there has to be a cleaner way of doing this....

var time = _mp.Time;
_mp.Stop();
_media.AddOption(string.Format(@":sub-track-id={0}", 2));
_mp.Play();
_mp.Time = time;

Any ideas on how to clean this up and toggle subtitles on and off during playback?

Solution

_mp.SetSpu(-1);

SPU (Sub Picture Unit) means essentially subtitles in VLC jargon.

You can get more info about subtitles tracks with the following property which returns an array of the spu tracks:

_mp.SpuDescription

The first one should be the "disable" option and have a -1 ID.