There are many ways notifying on property changed, and I think the most popular one is using the lambda expression solution: public class Ball : Model { private double _velocity; public double Velocity { get { return _velocity; } set { if (_velocity != value ) { _velocity = value ; NotifyPropertyChanged(() => Velocity); } } } } I’ve to say that using the lambda solution is cool and type safety. But, why should I bother creating a field member for each property, set it only if not equals to the...