Exposing an ISO C++ class to C#

Question

I need to expose some C++ classes to C# (I am building on Linux, using mono, so COM is not an option)

The evidence I have gathered so far suggests that the best way to approach this is:

Write a wrapper C++.Net class around the ISO C++ class
Consume the C++.Net classes from C#

I have the following questions:

First, is this the "best" way of achieving the goal of exposing ISO C++ classes to C# ?
So far though, I have not seen any examples that actually show how to do this - can anyone suggest some links, or a code snippet to show how this is done for a dummy class?
How may I send asynchronous message notifications from the C++ code to the C# code ?. Ideally, I would like to cause the C# class to raise an event, with the received data as an argument

I agree with Reed Copsey. Basically write a C wrapper around the C++ library and then use C# to interface with the C wrapper using P/Invoke. I find the following reference extremely useful when inter-operating with native libraries : mono-project.com/Interop_with_Native_Libraries — Frank Hale
– Frank Hale, Commented Apr 7, 2010 at 21:03

roalz · Accepted Answer · 2017-03-21 14:32:46Z

You can't do C++/.NET classes on Linux using Mono. Mono doesn't support Managed C++ or C++/CLI, so there is no way to "Write a wrapper C++.Net class around the ISO C++ class".

Your best option for this is to generate a C API for your C++ class, which can be accessed via Platform Invoke.

That being said, one option for easing this is to use SWIG to generate the wrappers for you. It supports generation of C# wrappers from C++ classes (as well as wrappers to other languages), and works well on Linux/Mono.

Edit:

For an official "Mono doesn't support mixed mode C++/CLI", see the Languages page:

It's important to note that any language that compiles to pure IL should work under Mono. Some languages such as Microsoft's Managed C++ do not always compile to pure IL, so they will not always work as expected, since they are not truly platform independent.

C++/CLI for native interop requires non-pure IL, so it will not work on Mono.

@Reed: are you sure about not being able to use C++/.Net? Could you send me the link please - I need to show it to someone who insists that it is possible
@Stick it to THE MAN: Here's a SO answer from a Mono dev: stackoverflow.com/questions/183377/… I'll see if I can find a more "offical" source, but it isn't supported.
@Stick it to THE MAN: I edited my answer to show you more details - Mono's language page discusses this, right at the top.
This is now possible on Mono. Mixed-mode C++/CLI is still not supported but they have their own way of integrating with native C++.
I agree with @Justin that Mono's CXXI is even more suitable for inter-operation between the two worlds, as it does not require a strange C++ alike language extension.

Justin · Accepted Answer · 2012-02-12 07:45:25Z

Mono has recently made some pretty big strides with C++ interoperability in CXXI (pronounced sexy).

From this posting, the short story is that the new CXXI technology allows C#/.NET developers to:

Easily consume existing C++ classes from C# or any other .NET language
Instantiate C++ objects from C#
Invoke C++ methods in C++ classes from C# code
Invoke C++ inline methods from C# code (provided your library is compiled with -fkeep-inline-functions or that you provide a surrogate library)
Subclass C++ classes from C#
Override C++ methods with C# methods
Expose instances of C++ classes or mixed C++/C# classes to both C# code and C++ as if they were native code.

CXXI is the result of two summers of work from Google's Summer of Code towards improving the interoperability of Mono with the C++ language.

Ajit Vaze · Accepted Answer · 2021-08-05 07:15:09Z

You have to write a C++ managed wrapper around your ISO C++ class like this

public ref class MyWrapper { public: MyWrapper (void) { pObj = new CMyUnmanagedClass(); } ~MyWrapper (void) { delete pObj; } int foo(void) { //pass through to the unmanaged object return pObj->foo(); } private: CMyUnmanagedClass* pObj; };

I hope this helps, Regards

This does not work on Linux/Mono. There is no support for mixed mode assemblies (or C++/CLI at all) with Mono.

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Exposing an ISO C++ class to C#

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