Why .NET doesn't have built-in Observer pattern like Java?

Question

I wonder why .NET framework doesn't have pair (Observer/Observable) interfaces similar to Java's feature?

EDIT: yes i know about events and delegates but using those interfaces is a simple and bookish approach of this DP isn't it?

Answer 1

In .NET 4 it does: System.IObservable<T> and System.IObserver<T> (which are a Dual of IEnumerable<T> and IEnumerator<T>). Look at the Reactive Extensions (Rx) project for compositional use of these interfaces with asynchronous events.

More generally, the Observer pattern is better served in .NET with events.