Sunday, September 01, 2013

Reactive Programming For .NET And C# Developers - An Introduction To IEnumerable, IQueryable, IObservable & IQbservable


Reactive Extensions are out there in the wild for some time, and in this post we should discuss Reactive extensions in a bit more detail. Also, in this post we'll touch IQbservables – the most mysteriously named thing/interface in the world, may be after Higgs Boson. Push and Pull sequences are everywhere – and now with the devices on one end and the cloud at the other end, most of the data transactions happen via push/pull sequences. Hence, it is essential to grab the basic concepts regarding the programming models around them.

First Things First

Let us take a step back and discuss IEnumerable and IQueryable first, before discussing further about Reactive IObservable and IQbservable (Qbservables = Queryable Observables – Oh yea, funny name).


As you may be aware, the IEnumerable model can be viewed as a pull operation. You are getting an enumerator, and then you iterate the collection by moving forward using MoveNext on a set of items till you reach the final item. And Pull models are useful when the environment is requesting data from an external source. To cover some basics - IEnumerable has a GetEnumerator method which returns an enumerator with a MoveNext() method and a Current property. Offline tip - A C# for each statement can iterate on any dumb thing that can return a GetEnumerator.  Anyway, here is what the non generic version of IEnumerable looks like.

public interface IEnumerable
    IEnumerator GetEnumerator();

public interface IEnumerator
    Object Current {get;}
    bool MoveNext();
    void Reset();

Read more: Codeproject
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