Example of a ViewModel used in C#/XAML MonoGame app

ScoreViewModel.cs

public class ScoreViewModel : BaseViewModel, IScoreViewModel  
{
    #region Properties

    private static IScoreViewModel _instance;
    public static IScoreViewModel Instance { get { return _instance ?? (_instance = new ScoreViewModel()); } }

    private float _distanceMax;
    public float DistanceMax
    {
        get
        {
            return _distanceMax;
        }
        set
        {
            _distanceMax = value;
            RaisePropertyChanged();
            RaisePropertyChanged("Score");
        }
    }

    private float _ballPoints;
    public float BallPoints
    {
        get
        {
            return _ballPoints;
        }
        set
        {
            _ballPoints = value;
            RaisePropertyChanged();
            RaisePropertyChanged("Score");
        }
    }

    public int Score { get { return (int)(_ballPoints * _distanceMax); } }

    #endregion


    #region Constructor

    private ScoreViewModel() { }

    #endregion
}