HOWTO: Expose an MFC OLE Container to VBA Automation

ID: Q189486

The information in this article applies to:

The Microsoft Foundation Classes (MFC), included with:
- Microsoft Visual C++, 32-bit Editions, version 5.0

SUMMARY

The Microsoft Visual Basic for Applications Container property returns a pointer to the container's dispatch interface. However, the MFC OLE container implementation does not support this behavior. When you attempt to access this property, you get the following Visual Basic for Applications error:

Run-time error 430, Class does not support automation.

This occurs even if automation support has been added to the container.

For example, in Microsoft Word, the Visual Basic for Applications code ThisDocument.Container should return the dispatch pointer of the container. Instead, when run while embedded inside an MFC container application, the above error is returned.

Support for this property is necessary for Visual Basic for Applications to have access to automation objects that might be exposed by your MFC OLE container application.

MORE INFORMATION

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

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.

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-&gt;GetDocument()->GetIDispatch(TRUE))
            return S_OK;
         else
            return E_FAIL;
         }
         return E_FAIL;
      }

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.)

REFERENCES

Visual C++ Programmer's Guide: search on "Automation Support, ClassWizard"

Microsoft Foundation Class Reference: MFC Technical Notes; TN038: MFC/OLE IUnknown Implementation

Platform SDK: search on: IServiceProvider

(c) Microsoft Corporation 1998, All Rights Reserved. Contributions by Mike Francis, Microsoft Corporation

Additional query words: IServiceProvider QueryService 430 Container Office Automation kbMFC kbOLE kbVC500

Keywords : kbcode
Version : WINNT:5.0
Platform : winnt
Issue type : kbhowto