How To Expose an MFC OLE Container to VBA Automation

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Steps to Expose a Dispatch Interface From an MFC OLE Container Application

1. Add automation to your container application. If you created your container with the AppWizard and you included automation support, this is already done. If you need to add automation support, see "ClassWizard: Automation Support" in the Visual C++ documentation.
2. Implement IServiceProvider. Since Visual Basic for Applications queries the container via COleClientItem for IServiceProvider, this interface should be implemented as a nested class of your COleClientItem derived class. (See code below.)
   
   Place the following code in the header file of your derived COleClientItem class:

         class CSomeClientItem : public COleClientItem
         {
         ...
         BEGIN_INTERFACE_PART(OleServiceProvider, IServiceProvider)
            INIT_INTERFACE_PART(CSomeClientItem, OleServiceProvider)
             STDMETHOD(QueryService)
             (REFGUID guidService, // Unique identifier for the requested
                                   // service.
             REFIID riid,    //Unique identifier for the requested interface.
             void** ppv);    //Address of output variable.
         END_INTERFACE_PART(OleServiceProvider)
         DECLARE_INTERFACE_MAP()
         ...
         };
   						

   Place the following code in the .cpp file of your derived ColeClientItem class:

         BEGIN_INTERFACE_MAP(CSomeClientItem, COleClientItem)
         INTERFACE_PART(CSomeClientItem,IID_IServiceProvider,
                        OleServiceProvider)
         END_INTERFACE_MAP()
   
         STDMETHODIMP_(ULONG) CSomeClientItem::XOleServiceProvider::AddRef()
         {
            METHOD_PROLOGUE_EX(CSomeClientItem, OleServiceProvider)
            return pThis->ExternalAddRef();
         }
   
         STDMETHODIMP_(ULONG) CSomeClientItem::XOleServiceProvider::Release()
         {
            METHOD_PROLOGUE_EX(CSomeClientItem, OleServiceProvider)
            return pThis->ExternalRelease();
         }
   
         STDMETHODIMP CSomeClientItem::XOleServiceProvider::QueryInterface(
         REFIID iid, LPVOID* ppvObj)
         {
            METHOD_PROLOGUE_EX(CSomeClientItem, OleServiceProvider)
            return pThis->ExternalQueryInterface(&iid, ppvObj);
         }
   
         STDMETHODIMP CSomeClientItem::XOleServiceProvider::QueryService(
         REFGUID guidService, REFIID riid, void** ppv)
         {
            METHOD_PROLOGUE_EX(CSomeClientItem, OleServiceProvider)
            if ((guidService == SID_SContainerDispatch)&&(IID_IDispatch ==
                                                          riid))
            {
            // In this example, automation support has been added to
            // the document.
            if (*(ppv) = (LPVOID) pThis->GetDocument()->GetIDispatch(TRUE))
               return S_OK;
            else
               return E_FAIL;
            }
            return E_FAIL;
         }
   					

3. Return dispatch interface in the IServiceProvider::QueryService() call. IServiceProvider::QueryService is called requesting the SID_SContainerDispatch service and the IID_IDispatch interface. The dispatch interface to your automation class should be returned in this call. (See CSomeClientItem::XOleServiceProvider::QueryService in the previous code.)