Question

Given the following code.

EventLoopScheduler scheduler = new EventLoopScheduler(ts => new Thread(ts));

BehaviorSubject<int> subject = new BehaviorSubject<int>(0);

subject
    .ObserveOn(scheduler)
    .CombineLatest(Observable.Interval(TimeSpan.FromSeconds(1), scheduler), (x, y) => x)                        
    .Subscribe(x => Debug.WriteLine(x));

subject.OnNext(1);

Why does it print?

0
1
0
1
0
1
...

Instead of:

0
1
1
1
1
1
...

Answer 1

First of all your output looks really strange. I would say both of them. I guess the output should be:

1
1
1
1
1

without 0. This is because of the first interval value will be produced in 1 second – definitely after you call subject.OnNext(1);

The other strage thing BehaviourSubject<int> – is it the UK version of the BehaviorSubject(Of T) ? 🙂 If you have your own BehaviourSubject implementation, then please extend your question with it.