Should a managed class that wraps a DirectSound interface be IDisposable?

Question

I'm writing a managed wrapper around DirectSound. (It's a simple partial wrapper that solves my specific problem and nothing more. Don't tell me about NAudio or whatever.) Should a managed class that wraps IDirectSound8 be IDisposable and why? Same question about IDirectSoundBuffer8.

Answer 1

Technically: yes. Practically: no. IDirectSound8 is a COM interface, they are very conveniently wrapped in .NET with a interop library. A CCW. That CCW manages the reference counts on the underlying COM coclass object. A CCW does not implement IDisposable, even though it very much hangs on to an unmanaged resource.

The reason it doesn't is because it is almost impossible to implement IDisposable correctly. A COM coclass implements multiple interfaces, creating one adds to the reference count. You would have to be 100% that all of those interface pointers are no longer in use before a dispose would be safe. That's very hard to do, those pointers get created in unexpected ways. Like using an indexed property of one of the interfaces, the intermediate interface pointer is never visible in your code.

This is not a real problem, the garbage collector takes care of the reference counts, the finalizer gets the job done. It is just that it takes a bit longer for the object to be released. If you want to implement it anyway then you can do so by calling Marshal.FinalReleaseComObject() in your Dispose() implementation. Just beware of the significantly increased risk for failure, hard to diagnose too.