C# Wrapper Around Unmanaged C++

Question

I see that there have been similar questions asked here regarding wrapping unmanaged C++ with C# but they all seem to be about specific implementation issues. I'd like to know what the general approach is when using C# and unmanaged C++.

For example, I have quite a few classes written in unmanaged C++ that I want to be able to use through .NET (ideally with VBA in Excel). I've been using managed C++/CLI to do this so far, however have noticed some oddities with the language that I'd rather avoid. Reading further it seems as though I could wrap my unmanaged C++ in C# and then have direct access to .NET (while completely avoiding managed C++/CLI). Is this possible and if so what's the best way to go about it? Thank you for the help.

Answer 1

You have three choices:

• Use a C++/CLI wrapper. The ideal solution if you're targeting .NET. You can access everything from the .NET world. You can wrap your C++ library with it, and then use it from C#/whatever.
• Ditch .NET, and make a COM wrapper, possibly with the help of ATL. It is a little more difficult, but you can call your code more easily from VBA/Excel. You'll still be able to call your COM classes from .NET if you want.
• Compile your code as a native DLL and use P/Invoke from C#. Note that this solution is tedious at best since nothing is automatic.

If your goal is really Excel/VBA, since you're going to make COM objects anyway, I'd go with option 2 and make COM classes directly using ATL. This bypasses .NET completely though, but using .NET to interface between C++ code and Excel has always been a hassle for me.

Answer 2

If you're wanting to avoid C++/CLI completely and use pure C# to access your native code, then it would have to be through direct P/Invoke, method by method. This is almost certainly not ideal if you have a large amount of unmanaged code.

Personally, I would think the "best" solution would be to continue using C++/CLI to write managed wrappers around your native code that expose the simplest possible public interfaces to reduce the complexity.