attempted to read or write protected memory - dllimport

attempted to read or write protected memory - dllimport

I'm having a problem trying to import a c++ dll into c#
I always get the error "attempted to read or write protected memory" when
I call the constructor of the dll class. I've been locking in other
solutions for the same answer but I couldn't found solution.
I decided to use a simple function to discard that the error came from the
c++ part but I'm having the same problem...
Here is my code:
main.cpp:
#include "main.h"
simple_dll::simple_dll(int num) : numero(num) {}
int simple_dll::getNumero() {
return this->numero;
}
extern "C" DLL_EXPORT BOOL APIENTRY DllMain(HINSTANCE hinstDLL, DWORD
fdwReason, LPVOID lpvReserved)
{
switch (fdwReason)
{
case DLL_PROCESS_ATTACH:
// attach to process
// return FALSE to fail DLL load
break;
case DLL_PROCESS_DETACH:
// detach from process
break;
case DLL_THREAD_ATTACH:
// attach to thread
break;
case DLL_THREAD_DETACH:
// detach from thread
break;
}
return TRUE; // succesful
}
main.h:
#ifndef __MAIN_H__
#define __MAIN_H__
#include <windows.h>
/* To use this exported function of dll, include this header
* in your project.
*/
#ifdef BUILD_DLL
#define DLL_EXPORT __declspec(dllexport)
#else
#define DLL_EXPORT __declspec(dllimport)