Best way to create a “run-once” time delayed function in C#

Question

I am trying to create a function that takes in an Action and a Timeout, and executes the Action after the Timeout. The function is to be non-blocking. The function must be

Answer 1

The model you have, using a one-shot timer, is definitely the way to go. You certainly don't want to create a new thread for every one of them. You could have a single thread and a priority queue of actions keyed on time, but that's needless complexity.

Calling Dispose in the callback probably isn't a good idea, although I'd be tempted to give it a try. I seem to recall doing this in the past, and it worked okay. But it's kind of a wonky thing to do, I'll admit.

You can just remove the timer from the collection and not dispose it. With no references to the object, it will be eligible for garbage collection, meaning that the Dispose method will be called by the finalizer. Just not as timely as you might like. But it shouldn't be a problem. You're just leaking a handle for a brief period. As long as you don't have thousands of these things sitting around un-disposed for a long period, it's not going to be a problem.

Another option is to have a queue of timers that remains allocated, but deactivated (i.e. their timeout and intervals set to Timeout.Infinite). When you need a timer, you pull one from the queue, set it, and add it to your collection. When the timeout expires, you clear the timer and put it back on the queue. You can grow the queue dynamically if you have to, and you could even groom it from time to time.

That'll prevent you from leaking one timer for every event. Instead, you'll have a pool of timers (much like the Thread Pool, no?).