C # and C ++ Interop (C ++ C # to call a dynamic link library)

1. Create a new C ++ DLL projects

CPlus.cpp:

#include "stdafx.h"

extern "C" __declspec(dllexport) void HelloWorld(char* name)
{
    name[0] = 'c';
}

stdafx.h:

#pragma once

#include "targetver.h"

#define WIN32_LEAN_AND_MEAN
#include <windows.h>
extern "C" __declspec(dllexport) void HelloWorld(char* name);

Compiling C ++ DLL project was 

2. Create a new C # project

using System;
using System.Collections.Generic;
using System.Linq;
using System.Runtime.InteropServices;
using System.Text;
using System.Threading.Tasks;

namespace CSharp
{
    class Program
    {
        [DllImport("kernel32.dll", CharSet = CharSet.Ansi)]
        static extern IntPtr LoadLibrary(string lpFileName);        //加载动态链接库
        [DllImport("kernel32.dll", CharSet = CharSet.Ansi)]
        static extern IntPtr GetProcAddress(IntPtr hModule, string lpProcName);     //获取接口地址
        [DllImport("kernel32", EntryPoint = "FreeLibrary", SetLastError = true, CharSet = CharSet.Ansi)]
        static extern bool FreeLibrary(IntPtr hModule);
        private delegate void DelegateHelloWorld(IntPtr a);

        private static void Main(string[] args)
        {
            IntPtr hModule = LoadLibrary(@"D:\MyProject\CSharp\CSharp\bin\Debug\Cplus.dll");
            IntPtr proc = GetProcAddress(hModule, "HelloWorld");

            Byte[] array = new Byte[100];
            array[0] = (byte)'a';
            array[1] = (byte)'b';
            array[2] = (byte)'c';
            IntPtr ptr = Marshal.UnsafeAddrOfPinnedArrayElement(array, 0);
            DelegateHelloWorld delegate1 = Marshal.GetDelegateForFunctionPointer(proc, typeof(DelegateHelloWorld)) as DelegateHelloWorld;

            delegate1(ptr);
            string str = Encoding.ASCII.GetString(array).Replace("\0", "");
            Console.WriteLine(str);


            Console.ReadLine();
        }
    }
}

The overall effect is C # incoming string abc, C ++ method to the first byte c, C # give cbc.

Each call between different languages ​​to be noted various data types length problem, there is selected 32-bit, 64-bit problem compile time. So use an array of data exchange is a better approach.

When you convert a string array to pay attention to coding format, it is common ASCII, ANSI, UTF8 and so on.