C++

Call c++ dll functions from c#

1. Create c++ proj ---- ensure your entrypoint class uses namespace std 
2. Add a function declared extern "C" __declspec(dllexport)
3. compile, and verify the exported function via dumpbin /exports
4. Create c# project ---- ensure your class using System.Runtime.InteropServices;
5. Reference the c++ dll function like [DllImport("CplusConsoleApp.dll"
6. specify callingConvention as C  (so c# can find the functions normal/friendly name)
7. Call the function (like ANY other normal c# managed function)

// CplusConsoleApp.cpp : Defines the entry point for the console application.
#include "stdafx.h"
#include <iostream>
using namespace std;

extern "C" __declspec(dllexport) void fun1(){
cout << "This is output from a c++ program function called fun1 \n";
}



C:\app\DLLs>dumpbin /exports c:\app\DLLs\CplusConsoleApp.dll
Microsoft (R) COFF/PE Dumper Version 12.00.21005.1
Copyright (C) Microsoft Corporation.  All rights reserved.
Dump of file c:\app\DLLs\CplusConsoleApp.dll
  File Type: DLL
   Section contains the following exports for CplusConsoleApp.dll
       00000000 characteristics
       58D17336 time date stamp Tue Mar 21 14:38:46 2017
        0.00 version
           1 ordinal base
           2 number of functions
           2 number of names
       ordinal hint RVA      name
          1    0 000012C0 fun1 = _fun1
   Summary
        1000 .data
        1000 .rdata
        1000 .reloc
        1000 .rsrc
        2000 .text


C:\app\DLLs>TestMisc.exe
This is output from a c++ program function called fun1

using System;
using System.Runtime.InteropServices;
namespace TestMisc {
    static class Program {
        [DllImport("CplusConsoleApp.dll", CallingConvention = CallingConvention.Cdecl)]
        public static extern void fun1();

        static void Main(string[] args) {
            fun1();
        }
}