Using PInvoke to access my C++ lib not working

[Kenneth Chin]

Hi,

I have a simple project in MS VS 2013 to test accessing a simple C++ function in Excel, using P/Invoke and Excel-DNA.

I successfully followed this tutorial to get P/Invoke working with a C++ library.

http://manski.net/2012/05/pinvoke-tutorial-basics-part-1/

But once I layered on the Excel-DNA to create the XLL Add-In I get this error:

External library could not be registered - Path: CSProject.dll

    Error: Could not load file or assembly 'file:///C:\Users\kchin\Documents\Visual Studio 2013\Projects\PInvokeTest\Debug\CSProject.dll' or one of its dependencies. An attempt was made to load a program with an incorrect format.

Any help is appreciated!

I've attached my whole project.

Here's my C++ 

CPPFunctions.h

#ifndef _CPPLIB_H_

#define _CPPLIB_H_

#ifndef MYAPI

#define MYAPI 

#endif

#ifdef __cplusplus

extern "C" {

#endif

MYAPI int kAdd(int a, int b);

#ifdef __cplusplus

}

#endif

#endif // _CPPLIB_H_

CPPFunctions.cpp

#include "CPPFunctions.h"

#include <stdio.h>

MYAPI int kAdd(int a, int b) {

//printf("%x\n", str);

return a + b;

}

C# Code

PInvokeTest.cs

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

using System.Runtime.InteropServices;

using ExcelDna.Integration;

namespace PInvokeTest

{

    class Program

    {

        //static void Main(string[] args)

        //{

        //    Console.WriteLine(kAdd(4, 4));

        //}

        [DllImport("CPPLib.dll"),ExcelFunction(Description="My first Excel-DNA function")]

        public static extern int kAdd(int a, int b);

    }

}

[Govert van Drimmelen]

Hi Kenneth,

You might like to check the following:

* The C# class that defines your (public static) function should be 'public'.

* The C++ project must be compiled for the right bitness for the Excel you're running under. The .xll file in the project you sent was for 64-bit Excel, but the C++ project you sent was 32-bit.

Then it worked fine on my machine (with 32-bit Excel) after doing an "Install-Package Excel-DNA" to install the Excel-DNA NuGet package into the CSProject project.

So basically it should work, and the error is likely some local issue.

Regards,

Govert

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From: exce...@googlegroups.com [exce...@googlegroups.com] on behalf of Kenneth Chin [kennet...@gmail.com]
Sent: 17 February 2015 06:36 PM
To: exce...@googlegroups.com
Subject: [ExcelDna] Using PInvoke to access my C++ lib not working

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[Kenneth Chin]

Hi Govert,

Thanks for the reply. 

I'm running on Win7 64-bit OS and using Excel 2013 64-bit. I'm unable to test on a 32-bit Excel.

I did some changes and am now stuck on this error in Excel after calling my function:

"A value used in the formula is of the wrong data type."

The changes I made:

• Made the C# class public
  
• In configuration manager, changed the C++ project to x64 by selecting New then Copy settings from Win32

The confusing thing is, after the above changes, I tried changing the C# project to Console Application and Platform target to x86, uncommented out Main to run as an executable off the command line it works. It won't work when I select Any CPU or x64 as the platform target. 

I get the error:

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

   at PInvokeTest.Program.kAdd(Int32 a, Int32 b)

Are you able to get it running on Excel 64-bit? 

Ken

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