MainViewModel.cs

public class MainViewModel : INotifyPropertyChanged {
    ...
    public TimeSpan Position { get; set; }

    public MainViewModel() {
        ...
        _videoPlayerStateMachine.Configure(VideoState.Playing)
               .OnActivate(OnStateEntry)
               .OnEntry(OnStateEntry)
               .Permit(VideoTrigger.Pause, VideoState.Paused)
               .Permit(VideoTrigger.Stop, VideoState.Stopped)
               .InternalTransition(VideoTrigger.Rewind, ()=> {
                   Position = Position.Subtract(TimeSpan.FromSeconds(5));
               })
               .InternalTransition(VideoTrigger.Forward, () => {
                   Position = Position.Add(TimeSpan.FromSeconds(5));
               });
    }
}