Lets start creating Observables.

The easiest way of creating a stream of observable is using Observable.Return (Make sure you get Rx-Main from Nuget packages before doing this. Also include using System.Reactive.Linq namespace).

What will this statement do?
Observable.Return(10);

This can be represented using the following 'marble diagram'

This will call OnNext(10)  of the observer only once and then will call OnCompleted();

So Lets write this piece of code:-

var myObservable =  Observable.Return(10);

Congratulations!! you have just written your first observable.


Now What do I do with it? Lets subscribe to it and use as I would use a stream of data:-

 Console.WriteLine("Subscribing to my first observable");
            myObseravle.Subscribe(
                x => { Console.WriteLine("Next Value: "+ x); }
                );

You should see something like this:-

Now lets see if OnCompleted was called. Lets add another piece of lambda as follows:-

            myObseravle.Subscribe(
                x => { Console.WriteLine("Next Value: " + x); },
                () => { Console.WriteLine("Sequence Completed"); }
                );


The new output:-

So we know that this behaves exactly as it was shown in the marble diagram.