C / C++ / MFC

#include <iostream>
#include "..\\MyDll\\MyDll.h"

using namespace std;
using namespace NS;

int Print(string str);
int main()
{
  NS::A* a = new NS::A(Print);
  NS::printDlgt("Hello World!"); 
}

int Print(string str)
{
  cout << str << endl;
  return 0;
}

#include "pch.h"
#include "MyDll.h"
namespace NS
{
  PrintDelegate printDlgt;
  A::A(PrintDelegate print_Dlgt)
  {
    NS::printDlgt = print_Dlgt;
  }
}

#include <iostream>
#ifndef MYDLL_H
#define MYDLL_H

//MYDLL_EXPORTS is set in C++\Preprocessor
#ifdef MYDLL_EXPORTS
#define MYDLL_API __declspec(dllexport)
#else
#define MYDLL_API __declspec(dllimport)
#endif


using namespace std;
typedef int (*PrintDelegate)(string str);

namespace  NS
{
  extern PrintDelegate printDlgt;
  class MYDLL_API A
  {
  public:
     A(PrintDelegate print_Dlgt);
  };
}
#endif