Why does Subject<T>.Dispose does not dispose current subscriptions?

Question

Hi I've been thinking for some time that Subject<T> disposes all the subscriptions based on it if you manually call its Dispose method. But I've recently found it doesn't work that way, it just clears its inner collection of observers and substitutes it with a DisposedObserver helper class instance.

I found myself a little confused about the behaviour, just assumed that the "normal" would be just propagate and dispose all the suscribers. Later, trying to figure out why is designed this way, I guessed a couple of reasons why they designed this way.

• The suscriber may be a composition that depents partially on the subject , so full propagation of disposal doesn't make sense. ie. Merge is not disposed just because one of the sources was disposed, as everyone expects.
• Subject.Dispose It is semantically equivalent to a continuation with Observable.Never from the side of the observer. The Subject.Dispose caller can also call OnComplete or OnError if wanted to signal error or completion before disposal (because they are on the same scope).

Edit Note: Sorry for the unclear question. I already understand how to use it, this was more a design question. Let me state it more clearly.

Why do you think the designers of Rx made Dispose behaviour that way?

(the two points above are my answer trial)

Answer 1

A subject should indicate it is done by sending OnComplete or possibly OnError. This is idiomatically and grammatically correct Rx. Subscribers are responsible for ending their subscriptions by disposing them. You should write Observables such that they clean up resources once they are "done" even if subscribers have not unsubscribed.