c++/cli interface header file

Question

I have a C++ project (visual studio 2010) which consists of native code and c++/cli code as well. I cant compile the whole project with /clr, so I just do it for the respective c++/cli files. My Problem is that a header file cant be compiled with /clr, but I want to make some c++/cli functions reusable within the whole project and therefor define the method prototypes in a header file to include it in every file where I need it. Is there a solution? I have tried to define some mixed code method prototypes in a header file, but /clr must be switched on for that to compile.

Here is my example:

Test.h

#include <Windows.h>
#include <vector>
#include <string>

using std::vector;
using std::string;

#include <msclr/marshal.h>

#pragma managed

using namespace msclr::interop;
using namespace System;
using namespace System::IO;
using namespace System::Runtime::InteropServices;

public ref class Test
{
public:
    int Foo();
};

Test.cpp

#include "Test.h"

int Test::Foo()
{
    return 4;
}

Intellisense is complaining with errors in Test.h like c++/cli must be enabled to use #using. But I think this is negligible and it would compile anyway.

Compilation aborts with a Linker Error (sry, i have german VS version)

Fehler  6   error LNK1255: Fehler bei Verknüpfung aufgrund von Metadatenfehlern.    
Fehler  4   error LNK2022: Fehler bei Metadatenoperation (8013118D) : Duplizierte Typen (_PROPSHEETPAGEA) wurden gefunden, aber die Typenlayoutinformationen sind nicht konsistent: (0x02000198).   
Fehler  5   error LNK2022: Fehler bei Metadatenoperation (8013118D) : Duplizierte Typen (_PROPSHEETPAGEW) wurden gefunden, aber die Typenlayoutinformationen sind nicht konsistent: (0x020001d1).   

I definitely dont have a duplicate class "Test" elsewhere, so I dont know where the duplicate comes from. What are typelayout informations and why are they not consistent?

Answer 1

I think you've all missed the point.

You can easily compile a native project with some /clr classes. (For example: A native DLL will still function like a native DLL, however, it can also be loaded into C#, and it's /clr compiled classes can then be accessed in C#.)

That's why such an option exist at the file level. (Right click .cpp: Properties->C\C++->Common Language Runtime Support- /clr)

The problem is:

Communicating between native\managed classes, since .H files cannot be set to use /clr, those cannot be used to reference a managed class elsewhere including other /clr files within the same project. (ie, you can create /clr files, but, they can't talk to each other, nor can you reference them within native portions of the project.)

The best solution I can find is to create a "glue" C# .dll file.

Create a new C# class library, add the Native DLL as a reference, then compile.

Now, in your native project, you can load the C# DLL, and access the natives /clr stuff through it. (The managed code you reference this way can be used with native\managed code.)

It's very possible, but, I cannot find a straightforward way to accomplish this.

That's what the topic is about, there seems to be no way to reference /clr classes due to header files not working when you set /clr at the file level. (ie, a header cannot contain /clr code unless the WHOLE project is set to /clr.)

There must be a way to reference /clr stuff without headers, or C++\CLI is just broken, I can easily load native code into /clr files by using pragma + headers, however, the reverse is looking impossible short of my "glue" solution.

That is what I believe this topic is about.

---

My method works, but, it's very tricky to get right, and compilation is a pain due to circular dependencies, etc,.

I really hope there is a proper way to do this, I've been looking, and my search led me here...

The real solution, would be to make .h files support /clr, then you could define your managed class in the header, and be able to freely reference it using standard methods, like include\using\pragma, etc,.