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Calling C# .NET methods from unmanaged C/C++ code

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13 Dec 2013CPOL1 min read 276.8K   11.9K   46   54
Describes with an example of how you can call C#.NET methods from unmanaged C++ code.

Introduction

For a number of reasons which I won't get into, I needed to use a C# .NET DLL from unmanaged code. I spent a long time looking for the answer before figuring it out. So I thought I'd post the example here to spread the word.

The way it works is fairly straightforward and requires three components:

  1. C# DLL doing whatever.
  2. Managed C++ DLL with exposed C function. This DLL will call your C# DLL methods. 
  3. Unmanaged C++ application/DLL which will call the exposed C function in the Managed C++ DLL.

Using the code

Create your C# DLL. The below example just shows a simple MessageBox and sets the result of the value based on OK or CANCEL.

C#
// ManagedClass.cs

// Any source code blocks look like this
//

using System;
using System.Collections.Generic;
using System.Text;
using System.Windows.Forms;
using System.IO;

namespace ManagedCSharp
{
    public static class ManagedClass
    {
        public static void ShowValue(ref int value)
        {
            DialogResult result = MessageBox.Show("C# Message Box", 
                    "C# Message Box", MessageBoxButtons.OKCancel);

            if (result == DialogResult.OK)
                value = 1;
            else
                value = 2;
            return;
        }
    }
}

Create a Managed C++ DLL and reference it in your C# project.

This exports your function ShowMessageBox in an unmanaged format.

Inside the exported function, call the Managed C++ method which calls your C# methods.

MC++
// ManagedDll.h

#pragma once

using namespace System;
using namespace System::Reflection;

namespace ManagedDll {    

    public ref class DoWork
    {
        public:void ShowCSharpMessageBox(int *value)
        {            
            ManagedCSharp::ManagedClass::ShowValue(*value);
            return;
        }
    };
}

__declspec(dllexport) void ShowMessageBox(int *value)
{
    ManagedDll::DoWork work;    
    work.ShowCSharpMessageBox(value);    
}

Create your unmanaged C or C++ DLL or EXE and call the exposed C++ method in your managed code.

In your unmanaged project setting, you will need to reference the ManagedDll.lib file created by the ManagedDll project and build time.

MC++
// TestApp.cpp : Defines the entry point for the console application.
//

#include "stdafx.h"
#include "conio.h"
#include <iostream>
#include <windows.h>

_declspec(dllexport) void ShowMessageBox(int *value);


int _tmain()
{
    int *result;

    ShowMessageBox(result);

    if(*result == 1)
        printf("Ok Was Pressed \n");
    else
        if(*result == 2)
            printf("Cancel Was Pressed \n");
        else
            printf("Unknown result \n");

    system("pause");

    return 0;
}

Find the attached full project which should build straight away. Built in Visual Studio 2008.

License

This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)


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Comments and Discussions

 
AnswerLinks in my past answer Pin
Sergey Alexandrovich Kryukov26-Dec-20 4:07
mvaSergey Alexandrovich Kryukov26-Dec-20 4:07 
GeneralRe: My vote of 1 Pin
David Thielen24-Mar-17 11:48
David Thielen24-Mar-17 11:48 
QuestionFramework-specific compiling error Pin
Member 1141304814-Feb-15 12:55
Member 1141304814-Feb-15 12:55 
QuestionTesting Problem Pin
Member 1141304813-Feb-15 8:45
Member 1141304813-Feb-15 8:45 
AnswerRe: Testing Problem Pin
Member 1209768521-Dec-16 4:13
Member 1209768521-Dec-16 4:13 
QuestionHow to response the event of managed class Pin
Adam Xiang10-Jul-14 20:35
Adam Xiang10-Jul-14 20:35 
AnswerRe: How to response the event of managed class Pin
Shawn-USA6-May-15 18:11
Shawn-USA6-May-15 18:11 
QuestionIs this possible in windows phone 8? Pin
Member 1062996111-Jun-14 0:18
Member 1062996111-Jun-14 0:18 
In my project I need to call c# method from my native c++(not managed) code in windows phone xaml application.
So is this possible in Windows Phone 8 app?
QuestionCan't get this to work, please help Pin
erezlevi5-May-14 9:46
erezlevi5-May-14 9:46 
AnswerRe: Can't get this to work, please help Pin
erezlevi6-May-14 2:41
erezlevi6-May-14 2:41 
GeneralRe: Can't get this to work, please help Pin
Stanley Wu20-Nov-14 8:14
Stanley Wu20-Nov-14 8:14 
AnswerRe: Can't get this to work, please help Pin
Member 1209768521-Dec-16 4:35
Member 1209768521-Dec-16 4:35 
QuestionGeneric and detailed solution Pin
Pragmateek10-Jan-14 5:06
professionalPragmateek10-Jan-14 5:06 
QuestionMy vote of 5 Pin
mlnlover1113-Dec-13 7:35
mlnlover1113-Dec-13 7:35 

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