Call c++ code in c# by a cli wrapper - c++-cli

Question

I have a c++ code that needs to be called in c# by a cli wrapper. I am stuck at the operator overloading part.
//this is my code
//Cppclass.h
#ifdef CPP_EXP_EXPORTS
#define CPP_EXP __declspec(dllexport)
#else
#define CPP_EXP __declspec(dllimport)
#endif
class CPP_EXP Cppclass;
CPP_EXP Cppclass operator-(Cppclass const &, Cppclass const &);
class CPP_EXP Cppclass
{
public:
friend CPP_EXP Cppclass operator-(Cppclass const &, Cppclass const &);
};
//this is my managed c++ code.
#include "Cppclass.h"
namespace Wrapper
{
public ref class cppwrapclass
{
public:
static cppwrapclass ^ operator-(cppwrapclass%A,cppwrapclass%B)
{
operator-(A.obj,B.obj);
return gcnew cppwrapclass();
}
private:
Cppclass *obj;
};
}
Its showing an intellisense error and not getting compiled.

Answer 1

You write a wrapper like this:
public ref class cppwrapclass
{
public:
cppwrapclass(Cppclass *obj)
: obj(obj)
{
}
~cppwrapclass()
{
this->!cppwrapclass();
}
!cppwrapclass()
{
if (obj)
{
delete obj;
obj = nullptr;
}
}
static cppwrapclass^ operator-(cppwrapclass% A, cppwrapclass% B)
{
return gcnew cppwrapclass(new Cppclass(*A.obj - *B.obj));
}
private:
Cppclass* obj;
};
A.obj is of type Cppclass*, therefore *A.obj is of type Cppclass, and *A.obj - *B.obj is a temporary Cppclass which needs to be moved to the heap in order to be referenced by the wrapper, hence the copy constructor call: new Cppclass(*A.obj - *B.obj).
The rest is the Dispose pattern and finalizer plumbing code.