There is a template for a C# add-in (also one for VB as well) that you can find under https://forum.solidworks.com/docs/DOC-1147. Maybe enough to get you started.
EPDM 2010 SP2
Thanks. I saw that and missed the fact that it included the C# template. In any event, my problem was that I did not add the interop DLL file to th 'Files' section of the Addin properties in the EPDM admin tool. Once I did that, everything worked as expected.
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