Can an IDispose objects not have an available Dispose method

Question

I am using FileHelpers in one project, and the class MultiRecordEngine

public sealed class MultiRecordEngine : EventEngineBase<object>, IEnumerable, IDisposable

This class implements IDisposable, BUT don't have a public Dispose method...

MultiRecordEngine eng = null; eng.Dispose(); // <---- Results in compilation error

Inspecting this class code on GitHub I can see the method implemented explicitly here, line 913:

void IDisposable.Dispose() { Close(); GC.SuppressFinalize(this); }

So... Why cannot I invoke the method? Is this intended, and if so, is it a good practice, and in what circumstances?

Seems like a pain in the rear, and counter-intuitive. I'd like to hear if anyone can offer some benefit to explicitly implementing IDisposable. — hatchet - done with SOverflow
– hatchet - done with SOverflow, Commented Aug 20, 2013 at 15:07
similar questions: stackoverflow.com/questions/3119288/… and stackoverflow.com/questions/5577252/… and stackoverflow.com/questions/408415/… — hatchet - done with SOverflow
– hatchet - done with SOverflow, Commented Aug 20, 2013 at 15:09
@hatchet A possible reason is that it is nice to have the Intellisense list uncluttered by Dispose() that will 99% of the time not be invoked directly. — Keith Payne
– Keith Payne, Commented Aug 20, 2013 at 15:21
@KeithPayne - except that having Dispose() appear in the Intellisense list may be the tip off needed to make the programmer aware that it's something that needs disposing. If it doesn't appear, they may just assume it doesn't implement IDisposable. — hatchet - done with SOverflow
– hatchet - done with SOverflow, Commented Aug 20, 2013 at 15:42
@hatchet: The primary case where explicit implementation makes sense is when a class implements an interface that implements IDisposable (e.g. IEnumerator<T>) but the Dispose method does nothing. Microsoft suggests that things with methods called e.g. Close, Shutdown, etc. may implement Dispose explicitly to suggest that it's redundant with those other methods, but I really dislike that pattern since there's nothing to indicate what methods are adequate substitutes for Dispose (some classes may keep resources after Close to allow for being re-opened). — supercat
– supercat, Commented Aug 20, 2013 at 18:42

Lee · Accepted Answer · 2013-08-20 15:02:04Z

5

It's implemented explicitly, so you need to cast to IDisposable:

((IDisposable)eng).Dispose();

explicitly implemented members are only accessible through the interface, not the implementing class.

answered Aug 20, 2013 at 15:02

Lee

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1 Comment

RMalke Over a year ago

Ashamed of myself. I always thought the explicitly implementation had no effect in the client code. Thanks

Keith Payne · Accepted Answer · 2013-08-20 15:07:02Z

First, you can invoke the method by casting to IDisposable:

((IDisposable)eng).Dispose();

You can also properly use the class in a using block:

using (MultiRecordEngine eng = new MultiRecordEngine()) { .. }

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