C#: How do you implement the observer pattern?

1public interface IObserver<T>
2{
3    void OnNext(T value);
4    void OnError(Exception error);
5    void OnCompleted();
6}
7
8public interface IObservable<T>
9{
10    IDisposable Subscribe(IObserver<T> observer);
11}

1var source = new TemperatureSensor();
2source.Subscribe(new TemperatureDisplay());