MediaPlayer.HasAudio property returns null

Question

I am trying to play audio only if it isn't already playing.

I use this method in my class :

private MediaPlayer mediaPlayer;

public bool HasAudio(){
  return mediaPlayer.HasAudio; // this returns null and it says property is readonly
}

Sound game = new Sound();
if (game.HasAudio() == false)//play sound

How do I get true or false value?

Edit: Sound class structure, Class instance

Answer 1

I think I get what's going on here.

Here, you're instantiating the Sound, and then calling HasAudio on it. At this point, it's trying to access its m_mediaPlayer field but it is null because you're only instantiating it in the Play method. As I suggested in my sidenote comment, you need to first instantiate the MediaPlayer either in the constructor or in the field declaration.

internal class Sound
{
    public bool HasAudio { get { return mediaPlayer.HasAudio; } }

    private MediaPlayer mediaPlayer = new MediaPlayer();

    public void Play(string fileName)
    {
        mediaPlayer.Open(new Uri(@"sounds/" + fileName, UriKind.RelativeOrAbsoute));
        mediaPlayer.Play();
    }

    public void Stop()
    {
        mediaPlayer.Stop();
    }
}