What is the expected behavior of a locally scoped Timer?

Question

Specifically, if you create an instance of a Timer in the local scope, and then return from that scope:

1) Will the timer still execute?

2) When would it be garbage collected?

I offer these two scenarios:

Timer timer = new Timer(new TimerCallback((state) => { doSomething(); }));
timer.Change((int)TimeSpan.FromSeconds(30), (int)TimeSpan.FromSeconds(30));
return;

And

Timer timer = new Timer(new TimerCallback((state) => { doSomething(); }));
timer.Change((int)TimeSpan.FromSeconds(30), Timeout.Infinite);
return;

Answer 1

The TimerCallback has a reference to the method DoSomething(), and therefore (in your example) to this but there is no live reference going the other way so it should get collected...eventually

Answer 2

The timer might or might not execute, depends on whether garbage collection runs before the time executes. This is why it's good practice to keep a reference to the timer somewhere other than on the stack.

Note that this is not always problematic; for example, threads won't be collected as long as they are still running.