调用C ++导出函数在C＃ [英] Call C++ Exported Function in C#

问题描述

我有以下C ++代码：

I have the following C++ code:

#pragma once
#include "StdAfx.h"
#include <string>
using namespace std;
using namespace System;


extern "C" __declspec( dllexport ) string __stdcall GetVale()
{
    return "test";
}

我试图在C＃中调用这个函数：

I am trying to call this function in C# by doing this:

    [DllImport("Security.dll", CallingConvention = CallingConvention.StdCall, ExactSpelling = true, EntryPoint = "_GetVale@4")]
    internal static extern string Getvalue();

我这样做只是为了学习和理解真的。当我调用这个我得到一个PInvoke异常说我CallingConvention是不正确的。我相信我的错误在我的文件是非常小的。我知道切入点是_GetVale @ 4，因为我使用一个程序来找到它。如果我不能改变它到任何东西它抛出一个入口点没有找到，所以我的问题是其他地方。

I am doing this just to learn and understand really. When I call this I get a PInvoke exception saying my CallingConvention is not correct. I am sure my mistakes in my files are very small. I know the entry point is "_GetVale@4" for I used a program to find it. If I can't change that to anything else it throws a entry point not found, so my problem is some where else.

我做错了什么？谢谢！

推荐答案

不能对使用C ++类型的函数使用简单的p调用。您应该限制自己使用纯c。

You can't use simple p-invoke for functions that use C++ types. You should restrict yourself to pure c.

返回 char * 很少是正确的解决方案。

Returning a char* is rarely the correct solution. You get lifetime issues: It's unclear when and how the return value should be freed.

一个标准模式是调用者传递一个 char *

One standard pattern is the caller passing in a char* and a length, and the callee filling this buffer.

C

extern "C" __declspec( dllexport ) void __stdcall GetValue(char* buf, in length)

C＃

[DllImport("Security.dll", CallingConvention = CallingConvention.StdCall, Charset = CharSet.Ansi]
internal static extern void GetValue(StringBuilder buf, int length);

---

有几种直接使用C ++的方法：

---

There are a few ways to work with C++ directly:

1. 创建SWIG包装器


2. 使用CXXI

这是一个有点恼人的工作，它需要一个C +边的包装器CXXI听起来很有趣，但我没有自己使用。

I'm not too fond of SWIG. It's a bit annoying to work with, and it requires a C++ sided wrapper. CXXI sounds interesting, but I haven't used it myself.

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