Sharing objects between C# and C++ code

Question

Is it possible to share references to C# objects between C# and C++ code without massive complexity? Or is this generally considered a bad idea?

Answer 1

The best solution for sharing a C# object between native and managed code is to use COM interop. This allows you to essentially share an interface of an object between managed code and it's equivalent signature in C++.

As for the complexity side of things. The majority of COM interop scenarios are straight forward and really are no more complex than good old COM programming. On the managed side it looks really no different than a normal interface.

Once you introduce multiple threads or start playing around between COM apartments though, things can get a bit tricky.

In my experience, the easiest way to get this working is the following.

• Define an interface in C# that you wish to use in C++
• Mark the interface with the ComVisible(true) attrbute
• Run tlbexp on the assembly which generates a TLB file
• Import the TLB into your native project

This will get the interface definition into both of your projects. How to pass that between the projects requires a bit more detail into your architecture.

Answer 2

Another solution I can recommend, from personal experience, is to use a managed C++ interface between the two if the C++ code you want to access is too large or too complex.

For example, I am using the RakNet C++ network library in a C# project. The solutions are to either create a massive wrapper class in C# to access the required C++ functions, create a C++ wrapper around those functions which can than be used as a COM interop or use Managed C++ (Visual C++/CLI).

I chose the latter which allows me to use C++ to access the RakNet library, but the classes created can be used directly in another .NET project as if. So the main logic has been created in those Managed C++ classes, which also allow me to use the .NET framework and some of its wonderful features. In my C# project I simply need to call the Managed C++ library which provides me with all in all 20 functions I need to perform everything.