一个COM示例程序

void CEx24cView::OnTestSpaceship() 
{
    CLSID clsid;
    LPCLASSFACTORY pClf; 
    LPUNKNOWN pUnk;
    IMotion* pMot;
    IVisual* pVis;
    HRESULT hr;

    if ((hr = ::CLSIDFromProgID(L"Spaceship", &clsid)) != NOERROR) 
    {
        TRACE("unable to find Program ID -- error = %x/n", hr);
        return;
    }
    if ((hr = ::CoGetClassObject(clsid, CLSCTX_INPROC_SERVER,
        NULL, IID_IClassFactory, (void **) &pClf)) != NOERROR) {;
        TRACE("unable to find CLSID -- error = %x/n", hr);
        return;
    }

    pClf->CreateInstance(NULL, IID_IUnknown, (void**) &pUnk);
    pUnk->QueryInterface(IID_IMotion, (void**) &pMot); // All three
    pMot->QueryInterface(IID_IVisual, (void**) &pVis); //  pointers
                                                       //  should work
    TRACE("main: pUnk = %p, pMot = %p, pDis = %p/n", pUnk, pMot, pVis);
    
    // Test all the interface virtual functions
    pMot->Fly();
    int nPos = pMot->GetPosition();
    TRACE("nPos = %d/n", nPos);
    pVis->Display();

    pClf->Release();
    pUnk->Release();
    pMot->Release();
    pVis->Release();
    AfxMessageBox("Test succeeded. See Debug window for output.");
}

// interface.h

struct IMotion : public IUnknown
{
    STDMETHOD_(void, Fly) () = 0;
    STDMETHOD_(int&, GetPosition) () = 0;
};

struct IVisual : public IUnknown
{
    STDMETHOD_(void, Display) () = 0;
};

// Spaceship.h : header file

Code

void ITrace(REFIID iid, const char* str);

/////////////////////////////////////////////////////////////////////////////
// CSpaceship command target

class CSpaceship : public CCmdTarget
{
    DECLARE_DYNCREATE(CSpaceship)
private:
    int m_nPosition; // We can access this from all the interfaces
    int m_nAcceleration;
    int m_nColor;
protected:
    CSpaceship();           // protected constructor used by dynamic creation

// Attributes
public:

// Operations
public:

// Overrides
    // ClassWizard generated virtual function overrides
    //{{AFX_VIRTUAL(CSpaceship)
    public:
    virtual void OnFinalRelease();
    //}}AFX_VIRTUAL

// Implementation
protected:
    virtual ~CSpaceship();

    // Generated message map functions
    //{{AFX_MSG(CSpaceship)
        // NOTE - the ClassWizard will add and remove member functions here.
    //}}AFX_MSG

    DECLARE_MESSAGE_MAP()
    DECLARE_OLECREATE(CSpaceship)

    BEGIN_INTERFACE_PART(Motion, IMotion)
        STDMETHOD_(void, Fly) ();
        STDMETHOD_(int&, GetPosition) ();
    END_INTERFACE_PART(Motion)
    
    BEGIN_INTERFACE_PART(Visual, IVisual)
        STDMETHOD_(void, Display) ();
    END_INTERFACE_PART(Visual)

    DECLARE_INTERFACE_MAP()
};

// Spaceship.cpp : implementation file

Code
//////////////////////////////////////////////////////////////////////
// CSpaceship

// {692D03A4-C689-11CE-B337-88EA36DE9E4E}
static const IID IID_IMotion =
{ 0x692d03a4, 0xc689, 0x11ce,
    { 0xb3, 0x37, 0x88, 0xea, 0x36, 0xde, 0x9e, 0x4e } };

// {692D03A5-C689-11CE-B337-88EA36DE9E4E}
static const IID IID_IVisual =
{ 0x692d03a5, 0xc689, 0x11ce,
    { 0xb3, 0x37, 0x88, 0xea, 0x36, 0xde, 0x9e, 0x4e } };

IMPLEMENT_DYNCREATE(CSpaceship, CCmdTarget)

CSpaceship::CSpaceship()
{
    TRACE("CSpaceship ctor/n");
    m_nPosition = 100;
    m_nAcceleration = 101;
    m_nColor = 102;
    // To keep the application running as long as an OLE automation
    //   object is active, the constructor calls AfxOleLockApp.
    
    AfxOleLockApp();
}

CSpaceship::~CSpaceship()
{
    TRACE("CSpaceship dtor/n");
    // To terminate the application when all objects created with
    //   OLE automation, the destructor calls AfxOleUnlockApp.
    
    AfxOleUnlockApp();
}

void CSpaceship::OnFinalRelease()
{
    // When the last reference for an automation object is released
    //   OnFinalRelease is called. This implementation deletes the 
    //   object. Add additional cleanup required for your object before
    //   deleting it from memory.

    delete this;
}


BEGIN_MESSAGE_MAP(CSpaceship, CCmdTarget)
    //{{AFX_MSG_MAP(CSpaceship)
    // NOTE - the ClassWizard will add and remove mapping macros here.
    //}}AFX_MSG_MAP
END_MESSAGE_MAP()

BEGIN_INTERFACE_MAP(CSpaceship, CCmdTarget)
    INTERFACE_PART(CSpaceship, IID_IMotion, Motion)
    INTERFACE_PART(CSpaceship, IID_IVisual, Visual)
END_INTERFACE_MAP()

// {692D03A3-C689-11CE-B337-88EA36DE9E4E}
IMPLEMENT_OLECREATE(CSpaceship, "Spaceship", 0x692d03a3, 0xc689,
                    0x11ce, 0xb3, 0x37, 0x88, 0xea, 0x36, 0xde,
                    0x9e, 0x4e)

STDMETHODIMP_(ULONG) CSpaceship::XMotion::AddRef()
{
    TRACE("CSpaceship::XMotion::AddRef/n");
    METHOD_PROLOGUE(CSpaceship, Motion)
    return pThis->ExternalAddRef();
}

STDMETHODIMP_(ULONG) CSpaceship::XMotion::Release()
{
    TRACE("CSpaceship::XMotion::Release/n");
    METHOD_PROLOGUE(CSpaceship, Motion)
    return pThis->ExternalRelease();
}

STDMETHODIMP CSpaceship::XMotion::QueryInterface(
    REFIID iid, LPVOID* ppvObj)
{
    ITrace(iid, "CSpaceship::XMotion::QueryInterface");
    METHOD_PROLOGUE(CSpaceship, Motion)
    return pThis->ExternalQueryInterface(&iid, ppvObj);
}


STDMETHODIMP_(void) CSpaceship::XMotion::Fly()
{
    TRACE("CSpaceship::XMotion::Fly/n");
    METHOD_PROLOGUE(CSpaceship, Motion)
    TRACE("m_nPosition = %d/n", pThis->m_nPosition);
    TRACE("m_nAcceleration = %d/n", pThis->m_nAcceleration);
    return;
}

STDMETHODIMP_(int&) CSpaceship::XMotion::GetPosition()
{
    TRACE("CSpaceship::XMotion::GetPosition/n");
    METHOD_PROLOGUE(CSpaceship, Motion)
    TRACE("m_nPosition = %d/n", pThis->m_nPosition);
    TRACE("m_nAcceleration = %d/n", pThis->m_nAcceleration);
    return pThis->m_nPosition;
}

//////////////////////////////////////////////////////////////////////
STDMETHODIMP_(ULONG) CSpaceship::XVisual::AddRef()
{
    TRACE("CSpaceship::XVisual::AddRef/n");
    METHOD_PROLOGUE(CSpaceship, Visual)
    return pThis->ExternalAddRef();
}

STDMETHODIMP_(ULONG) CSpaceship::XVisual::Release()
{
    TRACE("CSpaceship::XVisual::Release/n");
    METHOD_PROLOGUE(CSpaceship, Visual)
    return pThis->ExternalRelease();
}

STDMETHODIMP CSpaceship::XVisual::QueryInterface(
    REFIID iid, LPVOID* ppvObj)
{
    ITrace(iid, "CSpaceship::XVisual::QueryInterface");
    METHOD_PROLOGUE(CSpaceship, Visual)
    return pThis->ExternalQueryInterface(&iid, ppvObj);
}

STDMETHODIMP_(void) CSpaceship::XVisual::Display()
{
    TRACE("CSpaceship::XVisual::Display/n");
    METHOD_PROLOGUE(CSpaceship, Visual)
    TRACE("m_nPosition = %d/n", pThis->m_nPosition);
    TRACE("m_nColor = %d/n", pThis->m_nColor);
}

//////////////////////////////////////////////////////////////////////
void ITrace(REFIID iid, const char* str)
{
    OLECHAR* lpszIID;
    ::StringFromIID(iid, &lpszIID);
    CString strTemp = (LPCWSTR) lpszIID;
    TRACE("%s - %s/n", (const char*) strTemp, (const char*) str);
    AfxFreeTaskMem(lpszIID);
}

正规DLL部分代码

/////////////////////////////////////////////////////////////////////////////
// CEx24bApp initialization

BOOL CEx24bApp::InitInstance()
{
    // Register all OLE server (factories) as running.  This enables the
    //  OLE libraries to create objects from other applications.
    COleObjectFactory::RegisterAll();

    return TRUE;
}

/////////////////////////////////////////////////////////////////////////////
// Special entry points required for inproc servers

STDAPI DllGetClassObject(REFCLSID rclsid, REFIID riid, LPVOID* ppv)
{
    AFX_MANAGE_STATE(AfxGetStaticModuleState());
    return AfxDllGetClassObject(rclsid, riid, ppv);
}

STDAPI DllCanUnloadNow(void)
{
    AFX_MANAGE_STATE(AfxGetStaticModuleState());
    return AfxDllCanUnloadNow();
}

// by exporting DllRegisterServer, you can use regsvr.exe
STDAPI DllRegisterServer(void)
{
    AFX_MANAGE_STATE(AfxGetStaticModuleState());
    COleObjectFactory::UpdateRegistryAll();
    return S_OK;
}

要想运行客户端和组件程序，必须先注册组件来更新注册表，可以使用如下的代码：

BOOL CRegCompApp::InitInstance()
{
    SetRegistryKey(_T("Local AppWizard-Generated Applications"));
    // make sure to set Explorer options to allow DLLs to be visible
    CSpecialFileDialog dlgFile(TRUE, NULL, NULL, OFN_HIDEREADONLY | OFN_OVERWRITEPROMPT,
        "OCX files (*.ocx)|*.ocx|DLL files (*.dll)|*.dll||");
    dlgFile.m_ofn.lpstrTitle = "注册OCX/DLL File";
    if(dlgFile.DoModal() != IDOK)  return FALSE;
    CString strDllPath = dlgFile.GetPathName();//获取文件名
    // this wouldn't work for a dynamically linked Regular DLL
    HINSTANCE h = ::LoadLibrary(strDllPath);//加载dll
    if(h == NULL)
    {
        CString msg;
        msg.Format("Failed to find server %s", strDllPath);
        AfxMessageBox(msg);
        return FALSE;
    }
    FARPROC pFunc = ::GetProcAddress((HMODULE) h, "DllRegisterServer");
    if(pFunc == NULL) {
        AfxMessageBox("Failed to find DllRegisterServer function");
        return FALSE;
    }
    (*pFunc)();    // call the function to register the server 注册
    AfxMessageBox("Server registered OK");
    return FALSE;
}