I'm afraid I do not know the answer to your question.
However I have something which may prove interesting to you given that you
are creating a VS Addin.
I've not done much VS Studio Addin creation (at least in the official way)
because every time I've looked into it it seems very complex and cryptic
and seems to have lashings of COM all over it.
I found a framework for creating Managed Code plugins for studio which I
find very useful.
This framework is the DXCore by DevExpress (The guys who wrote CodeRush and
RefactorPro. In fact CodeRush and RefactorPro require theDXCore as they are
themeselves managed plugins for the DXCore) (
http://www.devexpress.com)
This may of course be overkill for your needs but I thought I'd mention it
in case it might help you.
If you're interested, there is a community forum supporting the DXCore athttp://community.devexpress.com/forums/181.aspx
Did I mention that the DXCore is a free download (Available fromhttp://
www.devexpress.com/Downloads/NET/IDETools/DXCore/
)
FWIW.. I am so happy working with the DXCore that my instinct is always to
look for a way to write my plugins in this way rather than using the MS way.
Your milage may of course vary