In my other question, I\'ve been trying to find someone who knows where to find free open source OCR library for C#. However, it seems there is only C++ library and obviously, C
You can get a good start here:
Call Unmanaged Code. Part 1 - Simple DLLImport
here's how I do it Interop. It shows you how to do the simple cases (BOOL to bool) as well as a bit of a harder case (passing a struct with pointers to managed memory). Good luck.
If you're wrapping is very simple, you can get away with P/Invoke. If you actually want managed objects, your easiest solution is probably to write the wrapper in C++/CLI (formerly Managed C++), as that provides a full feature set for managed/unmanaged interop.