How to do CreateFileMapping in a C++ DLL and access it in C#, VB and C++

// The following ifdef block is the standard way of creating macros which make exporting 
// from a DLL simpler. All files within this DLL are compiled with the SHAREDMEM_EXPORTS
// symbol defined on the command line. this symbol should not be defined on any project
// that uses this DLL. This way any other project whose source files include this file see 
// SHAREDMEM_API functions as being imported from a DLL, whereas this DLL sees symbols
// defined with this macro as being exported.
#ifdef SHAREDMEM_EXPORTS
#define SHAREDMEM_API __declspec(dllexport)
#else
#define SHAREDMEM_API __declspec(dllimport)
#endif

// This class is exported from the sharedmem.dll
class SHAREDMEM_API Csharedmem {
public:
	Csharedmem(void);
	// TODO: add your methods here.
};

extern SHAREDMEM_API int nsharedmem;

SHAREDMEM_API TCHAR* fnsharedmem(void);

const TCHAR szMapFileName[] = L"SHAREDMMF";