dadadax

using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using System.Runtime.InteropServices;

public class ADD_Script : MonoBehaviour {
    [DllImport("ADD")]
    private static extern int ADD_2(int A, int B);

    private readonly int _A = 1;

dadadax

#pragma once

#ifdef ADD_EXPORTS
#define ADD_API __declspec(dllexport)
#else
#define ADD_API __declspec(dllimport)
#endif

extern "C" {
	ADD_API int ADD_2(int A, int B);

dadadax

#include "ADD.h"

ADD_API int ADD_2(int A, int B) {
	return A + B;
}