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Understanding COM Event Handling

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9 Dec 2004CPOL19 min read 576.1K   7.4K   219  
Learn the fundamental principles of COM Event Handling via a C++ template class that allows for generic handling of dispinterface COM events.
// EventFiringObject.cpp : Implementation of DLL Exports.


// Note: Proxy/Stub Information
//      To build a separate proxy/stub DLL, 
//      run nmake -f EventFiringObjectps.mk in the project directory.

#include "stdafx.h"
#include "resource.h"
#include <initguid.h>
#include "EventFiringObject.h"

#include "EventFiringObject_i.c"
#include "EventFiringObject_Impl.h"


CComModule _Module;

BEGIN_OBJECT_MAP(ObjectMap)
OBJECT_ENTRY(CLSID_EventFiringObject, CEventFiringObject)
END_OBJECT_MAP()

/////////////////////////////////////////////////////////////////////////////
// DLL Entry Point

extern "C"
BOOL WINAPI DllMain(HINSTANCE hInstance, DWORD dwReason, LPVOID /*lpReserved*/)
{
    if (dwReason == DLL_PROCESS_ATTACH)
    {
        _Module.Init(ObjectMap, hInstance, &LIBID_EVENTFIRINGOBJECTLib);
        DisableThreadLibraryCalls(hInstance);
    }
    else if (dwReason == DLL_PROCESS_DETACH)
        _Module.Term();
    return TRUE;    // ok
}

/////////////////////////////////////////////////////////////////////////////
// Used to determine whether the DLL can be unloaded by OLE

STDAPI DllCanUnloadNow(void)
{
    return (_Module.GetLockCount()==0) ? S_OK : S_FALSE;
}

/////////////////////////////////////////////////////////////////////////////
// Returns a class factory to create an object of the requested type

STDAPI DllGetClassObject(REFCLSID rclsid, REFIID riid, LPVOID* ppv)
{
    return _Module.GetClassObject(rclsid, riid, ppv);
}

/////////////////////////////////////////////////////////////////////////////
// DllRegisterServer - Adds entries to the system registry

STDAPI DllRegisterServer(void)
{
    // registers object, typelib and all interfaces in typelib
    return _Module.RegisterServer(TRUE);
}

/////////////////////////////////////////////////////////////////////////////
// DllUnregisterServer - Removes entries from the system registry

STDAPI DllUnregisterServer(void)
{
    return _Module.UnregisterServer(TRUE);
}


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License

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


Written By
Systems Engineer NEC
Singapore Singapore
Lim Bio Liong is a Specialist at a leading Software House in Singapore.

Bio has been in software development for over 10 years. He specialises in C/C++ programming and Windows software development.

Bio has also done device-driver development and enjoys low-level programming. Bio has recently picked up C# programming and has been researching in this area.

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