1.專案整體結構如下：

2.定義標頭檔案dllpic.h

#ifndef DllTest_H_
#define DllTest_H_
#ifdef MYLIBDLL
#define MYLIBDLL extern "C" _declspec(dllimport) 
#else
#define MYLIBDLL extern "C" _declspec(dllexport) 
#endif
MYLIBDLL int _stdcall Add(int plus1, int plus2);
MYLIBDLL int _stdcall Minus(int plus1, int plus2);
//MYLIBDLL int  Add(int plus1, int plus2);
//You can also write like this:
//extern "C" {
//_declspec(dllexport) int Add(int plus1, int plus2);
//};

#endif
 

3.編寫原始檔dllpic.cpp，程式碼包含加減運算測試，方便學習。

#include<iostream>
#include<string>
#include<sstream>
#include"dllpic.h"
using namespace std;
#include "opencv2/opencv.hpp"
using namespace cv;
int _stdcall Add(int n1, int n2) {
   
	return (n1 + n2);
}

int _stdcall Minus(int n1, int n2) {
	return (n1 - n2);
}
 

4.編寫dllpic.def，將函式方法開放給外部程式呼叫

LIBRARY dllpic
EXPORTS Add Minus

5.C++自身呼叫測試程式碼：和普通的dll使用一樣，專案屬性包含目錄新增***.h所在目錄，庫目錄新增***.dll和***.lib所在目錄，連結器-輸入-附加依賴項要新增***.lib即可；測試程式碼。

// dllTest.cpp : 定義控制檯應用程式的入口點。
//

#include "stdafx.h"
#include<iostream>
#include "dllpic.h"
using namespace std;
int main()
{
	int a = 2;
	int b = 4;
	cout << Add(a, b) << endl;
	//
	char c;
	cin >> c;
    return 0;
}


	
 

 6.C#測試程式碼如下：

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Runtime.InteropServices;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace test
{ 
    public partial class Form1 : Form
    {
        [DllImport("jiaozhengPic.dll")]
        private extern static int Add(int n1, int n2);


        [DllImport("jiaozhengPic.dll")]
        private extern static int Minus(int n1, int n2);
        public Form1()
        {
            InitializeComponent();
        }

        private void Form1_Load(object sender, EventArgs e)
        {

        }
        private void button1_Click(object sender, EventArgs e)
        {
            int a1 = 10;

            int a2 = 12;

            int addH;
            addH = Add(a1, a2);
            MessageBox.Show(addH.ToString());
            addH=Minus(a1, a2);
            MessageBox.Show(addH.ToString());
        }
    }
}

 有興趣的朋友可以嘗試一下。