如何调用C ++ dll导出函数从c＃

问题描述

这是我第一次尝试混合c＃非托管C ++，这可能是一个非常简单的问题，但我不能得到它。

我需要从C ++ dll调用一些函数到C＃代码。下面是dll项目的代码：

.h文件：

  #pragma once 
 #include< iostream> 
 #if defined FIRSTDLL_EXPORTS 
 #define DECLDIR __declspec（dllexport）
 #else 
 #define DECLDIR __declspec（dllimport）
 #endif 
 
 externC
 {
 DECLDIR int Add（int a，int b）; 
 DECLDIR void Function（void）; 
} 
  

.cpp文件

  #includestdafx.h
 #includemyFct.h
 #include< iostream> 
 
 externC
 {
 DECLDIR int Add（int a，int b）
 {
 return（a + b）; 
} 
 
 DECLDIR void Function（void）
 {
 std :: cout< DLL Called！ << std :: endl; 
} 
} 
  

我编译了这个为调试和释放和复制它在我的C＃项目的 debug 文件夹中。

以下是c＃代码：

  DllImport（firstDLL.Dll）] 
 public static extern int Add（int a，int b）; 
 
 
 var cyu = Add（3，5）; 
  

当我尝试运行时，我得到

但是我看到的签名是一样的。我缺少什么？

谢谢！

解决方案

DLLImport的调用约定是stdcall，但是你的C ++代码的默认是cdecl。您看到的错误消息是当调用约定不匹配时显示的错误消息。这两个调用约定的参数堆栈清理要求是不同的，P / Invoke marshaller检测并报告这一点。

修复是使调用约定匹配。 / p>

例如，您可以这样更改您的P / Invoke：

  [DllImport（firstDLL.Dll，CallingConvention = CallingConvention.Cdecl）] 
 public static extern int Add（int a，int b）; 
  

另一个选项是更改您的C ++：

  #if defined FIRSTDLL_EXPORTS（returntype）
 #define DECLDIR __declspec（dllexport）returntype __stdcall 
 #else 
 #define DECLDIR __declspec（dllimport）returntype __stdcall 
 #endif 
  

显然，你应该只做其中一个。如果你改变两个C＃和C ++，你会有相同的问题反向！

如果我是你，我会把C ++代码作为cdecl，并更改C＃匹配。

This is the first time I'm trying to mix c# an unmanaged C++ so this might be a very simple question , but I don't get it.

I need to call some functions from a C++ dll into C# code. Here is the code for the dll project:

the .h file :

#pragma once
#include <iostream>
#if defined FIRSTDLL_EXPORTS
    #define DECLDIR __declspec(dllexport)
#else
    #define DECLDIR __declspec(dllimport)
#endif

extern "C"
    {
      DECLDIR int Add( int a, int b );
      DECLDIR void Function( void );
    }

the .cpp file

#include "stdafx.h"
#include "myFct.h"
#include <iostream>

extern "C"
{
      DECLDIR int Add( int a, int b )
      {
          return( a + b );
}

      DECLDIR void Function( void )
      {
          std::cout << "DLL Called!" << std::endl;
      }
}

I compiled this for both the debug and releas and copied it in the debug folder of my C# project. Neither version worked.

Here is the c# code:

[DllImport("firstDLL.Dll")]
public static extern int Add(int a, int b);


var cyu = Add(3, 5);

And when I try to run this I get

But as I see the signatures are the same. What am I missing??

Thanks!

解决方案

The default calling convention for DLLImport is stdcall, but the default of your C++ code is cdecl. The error message you have seen is what is shown when the calling conventions don't match. The parameter stack cleanup requirements are different for these two calling conventions, and the P/Invoke marshaller detects and reports this.

The fix is to make your calling conventions match.

For example you could change your P/Invoke like so:

[DllImport("firstDLL.Dll", CallingConvention = CallingConvention.Cdecl)]
public static extern int Add(int a, int b);

The other option is to change your C++:

#if defined FIRSTDLL_EXPORTS(returntype)
    #define DECLDIR __declspec(dllexport) returntype __stdcall
#else
    #define DECLDIR __declspec(dllimport) returntype __stdcall
#endif

Clearly you should only do one of these. If you change both C# and C++ you'll have the same problem in reverse!

If I were you I would leave the C++ code as cdecl and change the C# to match.

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