clr - Managed C++ to form a bridge between c# and C++

Question

I'm a bit rusty, actually really rusty with my C++. Haven't touched it since Freshman year of college so it's been a while.

Anyway, I'm doing the reverse of what most people do. Calling C# code from C++. I've done some research online and it seems like I need to create some managed C++ to form a bridge. Use __declspec(dllexport) and then create a dll from that and use the whole thing as a wrapper.

But my problem is - I'm really having a hard time finding examples. I found some basic stuff where someone wanted to use the C# version to String.ToUpper() but that was VERY basic and was only a small code snippet.

Anyone have any ideas of where I can look for something a bit more concrete? Note, I do NOT want to use COM. The goal is to not touch the C# code at all.

Answer 1

Create a new C++/CLI project in visual studio and add a reference to your C# dll. Assume we have a C# dll called DotNetLib.dll with this class in:

namespace DotNetLib
{
    public class Calc
    {
        public int Add(int a, int b)
        {
            return a + b;
        }
    }
}

Now add a CLR C++ class to your C++/CLI project:

// TestCPlusPlus.h

#pragma once

using namespace System;
using namespace DotNetLib;

namespace TestCPlusPlus {

    public ref class ManagedCPlusPlus
    {
    public:
        int Add(int a, int b)
        {
            Calc^ c = gcnew Calc();
            int result = c->Add(a, b);
            return result;
        }
    };
}

This will call C# from C++.

Now if needed you can add a native C++ class to your C++/CLI project which can talk to the CLR C++ class:

// Native.h
#pragma once

class Native
{
public:
    Native(void);
    int Add(int a, int b);
    ~Native(void);
};

and:

// Native.cpp
#include "StdAfx.h"
#include "Native.h"
#include "TestCPlusPlus.h"

Native::Native(void)
{
}

Native::~Native(void)
{
}

int Native::Add(int a, int b)
{
    TestCPlusPlus::ManagedCPlusPlus^ c = gcnew TestCPlusPlus::ManagedCPlusPlus();
    return c->Add(a, b);
}

You should be able to call the Native class from any other native C++ dll's as normal.

Note also that Managed C++ is different to and was superceeded by C++/CLI. Wikipedia explains it best:

http://en.wikipedia.org/wiki/C%2B%2B/CLI