Question

When would I implement IDispose on a class as opposed to a destructor? I read this article, but I’m still missing the point.

My assumption is that if I implement IDispose on an object, I can explicitly ‘destruct’ it as opposed to waiting for the garbage collector to do it. Is this correct?

Does that mean I should always explicitly call Dispose on an object? What are some common examples of this?

Answer 1

A finalizer (aka destructor) is part of garbage collection (GC) – it is indeterminate when (or even if) this happens, as GC mainly happens as a result of memory pressure (i.e. need more space). Finalizers are usually only used for cleaning up unmanaged resources, since managed resources will have their own collection/disposal.

Hence IDisposable is used to deterministically clean up objects, i.e. now. It doesn’t collect the object’s memory (that still belongs to GC) – but is used for example to close files, database connections, etc.

There are lots of previous topics on this:

• deterministic finalization
• disposing objects
• using block
• resources

Finally, note that it is not uncommon for an IDisposable object to also have a finalizer; in this case, Dispose() usually calls GC.SuppressFinalize(this), meaning that GC doesn’t run the finalizer – it simply throws the memory away (much cheaper). The finalizer still runs if you forget to Dispose() the object.