How to Interop between C# and C++

Question

I'm attempting a very basic interoperation between the 2 languages. I basically have some performance intensive code I wanna handle in C++ and then get the result back to my application.

All is going to be compiled in Visual Studio.

i have chosen int to be the input and output type since marshalling can be a bit wonky and not really what i'm dealing with.

C++ i have:

#include "stdafx.h" // default from vs2013, no idea what it is

_declspec(dllexport) int Diu(int p) {
    return p * 2;
}

C# i have:

using System;

namespace Interop {
    public class Program{
        [System.Runtime.InteropServices.DllImport("Hardworker.dll")]
        public static extern int Diu(int p);

        private static void Main(string[] args) {
            Console.WriteLine(Diu(2));
        }
    }
}

So it's a pretty basic example. But I'm getting the exception:

An unhandled exception of type 'System.BadImageFormatException' occurred in Interop.exe

Additional information: An attempt was made to load a program with an incorrect format. (Exception from HRESULT: 0x8007000B)

The C++ project is created as a Console Application > Dll in the create dialog. I checked the C++ dll in the disassembler and i can see a Diu as an exported symbol.

Uh. What did I miss about the setting up interop?

(or future reader) In addition to taking care to match platform (x86 vs x64, native C++ doesn't support AnyCPU), and name mangling, take care to also match the calling convention between the C++ code and the p/invoke declaration. — Ben Voigt
– Ben Voigt, Commented Jan 24, 2022 at 16:53

RedX · Accepted Answer · 2022-01-24 15:11:49Z

6

When you get this error: HRESULT: 0x8007000B is caused by platform incompatibility.
Check that that your compiler profile are set to the same platform(x86, x64 or AnyCPU).

edited Jan 24, 2022 at 15:11

RedX

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answered Nov 9, 2016 at 9:54

Tinwor

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3 Comments

CyberFox Over a year ago

Nice. I my computer is x64. I set compile to x86. And the error changed to EntryPointNotFoundException: Unable to find an entry point named 'Diu' in DLL 'Hardwork.dll'.

Yngve Hammersland Over a year ago

@CyberFox C++ mangles the function names based on parameter types, and other qualifiers of the function. You need to declare the function extern "C" for it to export with the name without mangling.

CyberFox Over a year ago

@YngveHammesrland that actually worked. 2 answers in 1.

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