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

"Managed Debugging Assistant 'PInvokeStackImbalance' has detected a problem in 'C:\Program Files\Microsoft Office\Office14\WINWORD.EXE'. Additional Information: A call to PInvoke function 'MyAddin!MyAddin.ThisAddIn::Add' has unbalanced the stack. This is likely because the managed PInvoke signature does not match the unmanaged target signature. Check that the calling convention and parameters of the PInvoke signature match the target unmanaged signature."

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

Thanks!

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.