How to debug unreleased COM references from managed code?

I have been searching for a tool to debug unreleased COM references, that usually cause e.g. Word/Outlook processes to hang in memory in case the code does not call Marshal.ReleaseCOMObject on all COM instances correctly. (Outlook 2007 partially fixes this for outlook addins, but this is a generic question).

Is there a tool that would display at least a list of COM references (by type) held by managed code? Ideally, it would also display memory profiler-style object trees helping to debug where the reference increment occured.

Debugging at runtime is not that important as being able to attach to a hung process - because the problem typically occurs when t开发者_开发知识库he code is done with the COM interface and someone forgot to release something - the application (e.g. winword) hangs in memory even after the calling managed application quits.

If such tool does not exist, what is the (technical?) reason? It would be very useful for debugging a lot of otherwise very hard to find problems when working with COM interop.

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Not quite the answer (or as simple as) you are looking for, but ReleaseCOMObject (as does the native Release which it wraps) returns an Integer which should indicate the number of outstanding references remaining. You could add code to your project to explicitly do an AddRef so you could then Release, and see the new count, and see if it is what you are expecting, etc.

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Here is my answer to debugging COM references using debugger

Troubleshooting a COM+ application deadlock