KnowledgeBase Archive

An Archive of Early Microsoft KnowledgeBase Articles

View on GitHub

Q154664: PRB: Dispatch Interface for Automation Object Must Be Registered

Article: Q154664
Product(s): Microsoft C Compiler
Version(s): winnt:4.0,4.1,4.2
Operating System(s): 
Keyword(s): kbole kbActiveX kbAutomation kbCOMt kbCtrlCreate kbMFC kbGrpDSMFCATL
Last Modified: 09-MAY-2001

-------------------------------------------------------------------------------
The information in this article applies to:

- Microsoft Visual C++, versions 4.0, 4.1 
- Microsoft Visual C++, 32-bit Enterprise Edition, version 4.2 
- Microsoft Visual C++, 32-bit Professional Edition, version 4.2 
-------------------------------------------------------------------------------

SYMPTOMS
========

Visual Basic 4.0 can do typesafe binding to automation objects. In this
scenario, the Visual Basic program will QueryInterface the automation object for
its dispatch interface. If the interface is not registered on the machine, the
Visual Basic program will fail to create the object. In this case, Visual Basic
will report the following error:

  Error 430: Class Does not Support OLE Automation.

MORE INFORMATION
================

Visual Basic does typesafe binding to an automation object when a variable is
dimensioned as a specific type. For instance:

  Dim x As New TestVB.Document

When developing this code, establish a reference to the TestVB module (in the
Visual Basic development environment, select Tools, References, and Browse for
the TestVB type library). Select the type library to register the type library
and the dispatch interface for the Document object.

The problem occurs when the Visual Basic program and the automation server are
loaded on a machine other than the development machine. Even if the automation
server is initially run to perform self-registration, the dispatch interface for
the automation object will not be registered and the "New" syntax will fail to
create the automation object.

To eliminate this problem, it is necessary to register the dispatch interface for
the automation object on the non-development machine. This can be done
programmatically or with a .reg file during setup.

In the case of the TestVB module, the Document object's dispatch interface is the
ITestVB interface, which is defined as follows in the .cpp file for the Document
object:

     // Note: We add support for IID_ITestVB to support typesafe binding
     // from VBA. This IID must match the GUID that is attached to the
     // dispinterface in the .ODL file.

     // {1249A4D2-D469-11CF-A68F-00AA00A70FC2}
     static const IID IID_ITestVB =
     { 0x1249a4d2, 0xd469, 0x11cf,
             { 0xa6, 0x8f, 0x0, 0xaa, 0x0, 0xa7, 0xf, 0xc2 } };

     BEGIN_INTERFACE_MAP(CTestVBDoc, CDocument)
         INTERFACE_PART(CTestVBDoc, IID_ITestVB, Dispatch)
     END_INTERFACE_MAP()

The following .reg file will register the ITestVB interface and enable marshaling
of the interface via the standard IDispatch proxy and stub.

     REGEDIT
     
     HKEY_CLASSES_ROOT\Interface\{1249A4D2-D469-11CF-A68F-00AA00A70FC2}
             = ITestVB
     HKEY_CLASSES_ROOT\Interface\{1249A4D2-D469-11CF-A68F-00AA00A70FC2}
             ProxyStubClsid = {00020420-0000-0000-C000-000000000046}
     HKEY_CLASSES_ROOT\Interface\{1249A4D2-D469-11CF-A68F-00AA00A70FC2}
             ProxyStubClsid32 = {00020420-0000-0000-C000-000000000046}

To programmatically register the interface, #include <winreg.h>, and insert
the following code (with the proper dispatch ID) in the InitInstance of the
automation server:

     HKEY key;

     // Open HKEY_CLASSES_ROOT
     RegOpenKey(HKEY_CLASSES_ROOT, _T("Interface"), &key);

     // Set up the key
     RegSetValue( key,
         _T("{1249A4D2-D469-11CF-A68F-00AA00A70FC2}"), REG_SZ,
         _T("ITestVB"), 0);
     RegSetValue( key,
         _T("{1249A4D2-D469-11CF-A68F-00AA00A70FC2}\\ProxyStubClsid"),
         REG_SZ, _T("{00020420-0000-0000-C000-000000000046}"), 0);
     RegSetValue( key,
         _T("{1249A4D2-D469-11CF-A68F-00AA00A70FC2}\\ProxyStubClsid32"),
         REG_SZ, _T("{00020420-0000-0000-C000-000000000046}"), 0);

     RegCloseKey(key);


Additional query words: Automation 430

======================================================================
Keywords          : kbole kbActiveX kbAutomation kbCOMt kbCtrlCreate kbMFC kbGrpDSMFCATL 
Technology        : kbVCsearch kbVC400 kbAudDeveloper kbVC410 kbVC420 kbVC32bitSearch
Version           : winnt:4.0,4.1,4.2
Issue type        : kbprb

=============================================================================

THE INFORMATION PROVIDED IN THE MICROSOFT KNOWLEDGE BASE IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND. MICROSOFT DISCLAIMS ALL WARRANTIES, EITHER EXPRESS OR IMPLIED, INCLUDING THE WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT SHALL MICROSOFT CORPORATION OR ITS SUPPLIERS BE LIABLE FOR ANY DAMAGES WHATSOEVER INCLUDING DIRECT, INDIRECT, INCIDENTAL, CONSEQUENTIAL, LOSS OF BUSINESS PROFITS OR SPECIAL DAMAGES, EVEN IF MICROSOFT CORPORATION OR ITS SUPPLIERS HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. SOME STATES DO NOT ALLOW THE EXCLUSION OR LIMITATION OF LIABILITY FOR CONSEQUENTIAL OR INCIDENTAL DAMAGES SO THE FOREGOING LIMITATION MAY NOT APPLY.