I am attempting to incorporate a 3rd party DLL that is unmanged into my
managed project. The problem as you might have guess is regarding getting a
callback to occur. The one big problem is that I don't have access to either
the code or the developer at this point hence my posting here.

I have been able to recreate the issue so I was hoping that someone could
tell me my issue. The code in the unmanaged DLL is basically this:

Header File:
#pragma once

typedef void (*__callbackroutine__)(BYTE byteOut);
typedef __callbackroutine__* CallbackRoutine;

extern "C"
{
   void __declspec(dllexport) Initialize(char* port_name, CallbackRoutine
cb);
}

Source File:
#include "stdafx.h"
#include "PinPadDllEx.h"

CallbackRoutine CallBack;

BOOL APIENTRY DllMain( HMODULE hModule,
                      DWORD  ul_reason_for_call,
                      LPVOID lpReserved)
{
   BOOL ret_val = TRUE;

   switch (ul_reason_for_call)
   {
       case DLL_PROCESS_ATTACH:
       case DLL_THREAD_ATTACH:
       case DLL_THREAD_DETACH:
       case DLL_PROCESS_DETACH:
           break;
   }

   return ret_val;
}

VOID CALLBACK TimerProc(HWND hwnd, UINT uMsg, UINT_PTR idEvent, DWORD
dwTime)
{
   ((void (*)(BYTE))CallBack)('A');
   return;
}

void Initialize(char* port_name, CallbackRoutine cb)
{
   CallBack = cb;

   int ret_val = SetTimer(NULL, NULL, 1000, TimerProc);
   return;
}

Source Code To Managed Container:
using System;
using System.Collections.Generic;
using System.Runtime.InteropServices;
using System.Text;
using System.Threading;

namespace TestPinPadDllEx
{
   public delegate void KeyPressedCB(Byte key);

   class Program
   {
       //public delegate void KeyPressedCB(Byte key);

       [DllImport("PinPadDllEx.dll", EntryPoint = "Initialize",
ExactSpelling = false, CharSet = CharSet.Ansi, CallingConvention =
CallingConvention.Cdecl)]

       public static void ProgramCB(Byte key)
       {
           System.Console.WriteLine("Key Press. Value: {0}", key);
           return;
       }

       static void Main(string[] args)
       {
           string comm_s = "COM5";

           KeyPressedCB cb = new KeyPressedCB(ProgramCB);

           Initialize(comm_s, cb);

           System.Threading.Thread.CurrentThread.Join();
           System.Console.WriteLine("Process exiting.");
           System.Console.ReadKey(true);
       }
   }

The "initialize" routine is called with good data. The issue is that the
TimerProc never gets called. It is not like I am getting an exception or GP.
Nothing happens. Obviously I am doing something wrong, but for the life of
me I can't figure it out.

By the way, I am using Visual Studio 2005 as my development system.

Many Thanks,

Tim