GC.Collect in a loop?

Question

I found this piece of code inside System.Web.ISAPIRuntime using Reflector

public void DoGCCollect()
{
    for (int i = 10; i > 0; i--)
    {
        GC.Collect();
    }
}

Can anyone comment on this? Is there a reason to do GC.Collect() in a loop? Why 10 times and not 3, 5 or 20? Analysis indicated that it's not used inside .net framework but it's public so I suppose that IIS could call it...

edit :

Just for clarification purposes : I have never called GC.Collect and I have no intentions of using it. I know it's a bad idea in most (if not all) cases. The question is why .net framework does it. Thanks for all your answers.

Answer 1

Looks truly horrible :)

Answer 2

Looks like someone with a doomsday complex wrote it with connotations that they'd be ending the world with a 10 second timer...

Answer 3

This is not a good idea because you really ought to trust the garbage collector to do its job without being invoked specifically from your code.

99.9% of the time you never need to call the GC from your code.

Answer 4

Yes, that's horrible. Firstly, you shouldn't need to do it at all. However, if you really want to force garbage collection as hard as you can, and wait for it to finish, you should probably use:

GC.Collect(GC.MaxGeneration, GCCollectionMode.Forced);
GC.WaitForPendingFinalizers();
// Collect anything that's just been finalized
GC.Collect(GC.MaxGeneration, GCCollectionMode.Forced);

Really not a nice idea though.

Answer 5

First of all it is not a good idea to call GC.Collect(). Calling it multiple times has little effect.

However, you sometimes see the pattern of calling Collect(), then WaitForPendingFinalizers(), and then finally Collect() again. The idea behind this is to ensure that instances with finalizers are also reclaimed, as they will survive the first collection. Keep in mind tough that this will induce a delay in the application and it should very rarely be needed.

Answer 6

I don't think you're going to get a better explanation that "one of Microsoft's programmers is pretty clueless, and apparently, no one else bothered to look at his code before it was checked in". ;)

It does look scary though.

It's a fairly common response to bugs you don't understand though. For whatever reason, you're trying to call the GC, and somehow, calling it doesn't seem to solve your problem (perhaps the real problem was just that you should wait for the finalizer thread or something), so the naive solution is obviously "Well, I'll just keep calling it then".

Similar to pressing 'print' repeatedly until your document is printed.

Perhaps you should submit it to thedailywtf.com though.

Answer 7

probably lsd or something..

Answer 8

Shouldn't things like this be pointed out to Microsoft? Would it do any good to post this on the Connect site?