Back in May 2005 I posted an article on how to mix C# and C++ code in single assembly.

I still get emails asking for samples.  So I created this simple sample. Enjoy.

We have this simple unmanaged C++ class UnmanagedFoo:

E:\sample\vc\mixed>more ufoo.h
#include <stdio.h>
class UnmanagedFoo
{
public:
    UnmanagedFoo() {printf("Constructing UnmanagedFoo\n");}
    ~UnmanagedFoo() {printf("Destructing UnmanagedFoo\n");}
   void ShowYourself();
};

And implementation:

E:\sample\vc\mixed>more ufoo.cpp
#include "ufoo.h"
void UnmanagedFoo::ShowYourself()
{
    printf("UnmanagedFoo\n");
}

Another simple C++/CLI class ManagedFoo, with a member of UnmanagedFoo.

E:\sample\vc\mixed>more mfoo.cpp
#include "ufoo.h"
#using <mscorlib.dll>
using namespace System;

ref class ManagedFoo
{
public:
    ManagedFoo()
    {
        Console::WriteLine("Constructing ManagedFoo");
        m_foo = new UnmanagedFoo();
        if (!m_foo) {
            throw gcnew OutOfMemoryException();
        }
    }
    ~ManagedFoo() {ShowDestruction();}
    !ManagedFoo() {ShowDestruction();}
    void ShowYourself()
    {
        Console::WriteLine("ManagedFoo");
        m_foo->ShowYourself();
    }
private:
    void ShowDestruction()
    {
        if (m_foo) {
            delete m_foo;
        }

        Console::WriteLine("Destructing ManagedFoo");
    }
    UnmanagedFoo *m_foo;
};

C# class Bar uses ManagedFoo:

E:\sample\vc\mixed>more bar.cs
using System;
class Bar
{
    public static void Main()
    {
        ManagedFoo foo = new ManagedFoo();
        foo.ShowYourself();
    }
}

Let us build the project.

First, compile ufoo.cpp into (unmanaged) obj file.

E:\sample\vc\mixed>cl.exe /Zi /MD /c ufoo.cpp
Microsoft (R) 32-bit C/C++ Optimizing Compiler Version 14.00.50727.42 for 80x86
Copyright (C) Microsoft Corporation.  All rights reserved.

ufoo.cpp

And mfoo.cpp

E:\sample\vc\mixed>cl.exe /Zi /clr /c mfoo.cpp
Microsoft (R) C/C++ Optimizing Compiler Version 14.00.50727.42
for Microsoft (R) .NET Framework version 2.00.50727.88
Copyright (C) Microsoft Corporation.  All rights reserved.

mfoo.cpp

And bar.cs, referencing mfoo.obj

E:\sample\vc\mixed>csc /target:module /addmodule:mfoo.obj bar.cs
Microsoft (R) Visual C# 2005 Compiler version 8.00.50727.88
for Microsoft (R) Windows (R) 2005 Framework version 2.0.50727
Copyright (C) Microsoft Corporation 2001-2005. All rights reserved.

Finally, let’s link everything together.

E:\sample\vc\mixed>link mfoo.obj ufoo.obj bar.netmodule /entry:Bar.Main /out:test.exe /subsystem:console /ltcg
Microsoft (R) Incremental Linker Version 8.00.50727.42
Copyright (C) Microsoft Corporation.  All rights reserved.

Generating code
Finished generating code

Now we have a single file assembly test.exe, mixed with unmanaged C++, C++/CLI, and C#.

E:\sample\vc\mixed>test
Constructing ManagedFoo
Constructing UnmanagedFoo
ManagedFoo
UnmanagedFoo
Destructing UnmanagedFoo
Destructing ManagedFoo

We can also put ufoo.obj into a lib and link the lib in the final step, instead of using ufoo.obj directly.

E:\sample\vc\mixed>lib ufoo.obj /out:ufoo.lib
Microsoft (R) Library Manager Version 8.00.50727.42
Copyright (C) Microsoft Corporation.  All rights reserved.

E:\sample\vc\mixed>link mfoo.obj ufoo.lib bar.netmodule /entry:Bar.Main /out:test2.exe /subsystem:console /ltcg
Microsoft (R) Incremental Linker Version 8.00.50727.42
Copyright (C) Microsoft Corporation.  All rights reserved.

Generating code
Finished generating code

E:\sample\vc\mixed>test2
Constructing ManagedFoo
Constructing UnmanagedFoo
ManagedFoo
UnmanagedFoo
Destructing UnmanagedFoo
Destructing ManagedFoo