There are several ways of doing it.
- PInvoke
- Create C++/CLI wrapper around your C++ native code (make static library out of C++ native code) and C++/CLI generated assembly can be easily utilized in .net application.
- COM, i.e using interop (which is difficult among all the options)
In my suggestion easiest way is to use option 2, but you need to take care of proper marshaling.