Tutorial - C# / Mono - C++ DLL Objects accessed from C#

#include <stdio.h>

extern "C"
{
__declspec(dllexport) void DisplayMessageFromDLL()
{
              printf ("Hi From the C DLL!\n");
}

__declspec(dllexport) int DisplayValueAndReturn(int i)
{
        printf("Value %i\n", i);
        return i+2;
}
}

using System;
using System.Runtime.InteropServices; // DLL support

namespace hellodlltest
{
class hellodllC
{
[DllImport("hellocdll.dll")]
public static extern void DisplayMessageFromDLL();

[DllImport("hellocdll.dll")]
public static extern int DisplayValueAndReturn(int i);

static void Main ()
        {
               Console.WriteLine ("C# program 'talking' to an C DLL");
DisplayMessageFromDLL();
Console.WriteLine(DisplayValueAndReturn(3).ToString());
Console.ReadLine()
        }
}
}