C#: Create strong reference between objects, without one referencing the other

Question

Suppose I have 2 classes, Foo and Bar. Foo does not have (and cannot have) a relation to Bar.

However, I want a bar instance to stay alive, as long as it\'s foo instance

Answer 1

Bar can only not be finalized if SOMETHING has a reference to it. Just have Foo tell that thing when it can let go of Bar.