Hi Jon,
[quote user="Jon Summers"]If you write a C# AddIn for MicroStation V8i then you are stuck with the VBA (COM) InterOp.[/quote]
it's not quite correct. It's possible to use C++/CLI to create wrappers around C++ native code, so the result will be assembly with NET API that can be referenced as a part of V8i NET addin.
Regards,
Jan