Step 1
Create a project in Xamarin iOS. New Project => Single View App. Give the Name
Step 2

Just Create a Media Player as you need. Add the following code in ViewDidLoad.
  1. public override void ViewDidLoad()
  2. {
  3. base.ViewDidLoad();
  5. //To listen changes in lock screen
  6. UIApplication.SharedApplication.BeginReceivingRemoteControlEvents();
  8. //creating an audio player with url
  9. mediaplayer = new AVPlayer(new Uri("https://www.soundhelix.com/examples/mp3/SoundHelix-Song-1.mp3"));
  11. //make audio play when app goes background
  12. AVAudioSession.SharedInstance().SetActive(true);
  13. AVAudioSession.SharedInstance().SetCategory(AVAudioSessionCategory.Playback);
  15. //Audio player Notification in lock screen
  16. MPNowPlayingInfo nowPlayingInfo;
  17. nowPlayingInfo = new MPNowPlayingInfo();
  18. nowPlayingInfo.Artist = "An OK Band";
  19. nowPlayingInfo.Title = "Our First Single!";
  21. // Register for receiving controls from lock screen and controlscreen
  22. MPNowPlayingInfoCenter.DefaultCenter.NowPlaying = nowPlayingInfo;
  23. }
Step 3
Now we have to listen to changes in that media player notification as the user taps on next, play/pause, or previous.
  1. public override void RemoteControlReceived(UIEvent theEvent)
  2. {
  3. base.RemoteControlReceived(theEvent);
  4. if (theEvent.Subtype == UIEventSubtype.RemoteControlPreviousTrack)
  5. {
  6. //Something you need to do.
  7. }
  8. else if (theEvent.Subtype == UIEventSubtype.RemoteControlNextTrack)
  9. {
  10. //Something you need to do.
  11. }
  12. else
  13. {
  14. //Something you need to do.
  15. }
  16. }
Step 4
For each time the audio or video has changed, we have to update in "nowPlayingInfo"
Step 5
That's all set. Now we are able to control our audio from the lock screen.