Question

I’ll create an observable (through a variety of means) and return it to interested parties, but when they’re done listening, I’d like to tear down the observable so it doesn’t continue consuming resources. Another way to think of it as creating topics in a pub sub system. When no one is subscribed to a topic any more, you don’t want to hold the topic and its filtering around anymore.

Answer 1

Rx already has an operator to suit your needs – well two actually – Publish & RefCount.

Here’s how to use them:

IObservable xs = ...

var rxs = xs.Publish().RefCount();

var sub1 = rxs.Subscribe(x => { });
var sub2 = rxs.Subscribe(x => { });

//later
sub1.Dispose();

//later 
sub2.Dispose();

//The underlying subscription to `xs` is now disposed of.

Simple.