Q197490: PRB: ATL Full Control Needs Enabled Stock Property for Access 97

Article: Q197490
Product(s): Microsoft C Compiler
Version(s): 5.0,6.0
Operating System(s): 
Keyword(s): kbnokeyword kbAccess97 kbATL210 kbCOMt kbContainer kbCtrlCreate kbVC500 kbVC600 kbATL30
Last Modified: 26-JUL-2002

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The information in this article applies to:

- Microsoft Visual C++, 32-bit Enterprise Edition, versions 5.0, 6.0 
- Microsoft Visual C++, 32-bit Professional Edition, versions 5.0, 6.0 
- Microsoft Visual C++, 32-bit Learning Edition, version 6.0 
- Microsoft Visual C++.NET (2002) 
- Microsoft Access 97 
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SYMPTOMS
========

When opening a form that was saved in Access 97 and contains ActiveX controls
developed with ATL, you might get a message box stating the following:

  There is no object in this control.

CAUSE
=====

This error can be caused when the control does not support the stock property
for Enabled.

RESOLUTION
==========

If you are developing a control using ATL and plan to use it in Microsoft
Access, be sure to support the Enabled stock property. The ATL COM Object Wizard
can add the needed code if you select Enabled from the list of available stock
properties on the last property page when inserting the full control.

If you already have a control project that does not have the Enabled stock
property selected, you can add support for it using the steps outlined here.

1. Determine whether or not your control has support for ANY stock properties.
  If not, modify the header file for the control to include support for ATL's
  default stock property support and comment out the IDispatchImpl derived
  class. For example:

  class ATL_NO_VTABLE CATLAccessKBControl :
    public CComObjectRootEx<CComSingleThreadModel>,
  //public IDispatchImpl<IATLAccessKBControl, &IID_IATLAccessKBControl,
  \    //&LIBID_ATLACCESSCONTROLLib>,
  public CStockPropImpl<CATLAccessKBControl, IATLAccessKBControl, \ 
            &IID_IATLAccessKBControl, &LIBID_ATLACCESSCONTROLLib>,
  //rest of interfaces that are derived....

2. Modify the IDL file by adding support for propget/propput methods for
  DISPID_ENABLED. For example:

  [
    object,
    uuid(91A905D0-8B9F-11D2-8F10-00C04F94089E),
    dual,
    pointer_default(unique)
  ]
  interface IATLAccessKBControl : IDispatch
  {
  [propput, id(DISPID_ENABLED)] HRESULT Enabled([in]VARIANT_BOOL
     vbool);
  [propget, id(DISPID_ENABLED)] HRESULT Enabled([out,retval] \ 
     VARIANT_BOOL*pbool);
  };

3. Add a member variable to the control's header file, which will have the
  enabled stock property value. For example:

  class ATL_NO_VTABLE CATLAccessKBControl :
    public CComObjectRootEx<CComSingleThreadModel>,
  //rest of interfaces that are derived...
  {
    public:
      BOOL m_bEnabled;
    //rest of class definition
  };

Be sure to name the property "m_bEnabled" so ATL framework correctly sets it.

STATUS
======

This behavior is by design.

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

You do not get this problem with controls created with MFC or Visual Basic. Both
of these products provide the Enabled stock property by default.

Steps to Reproduce Behavior
---------------------------

1. Create a new ATL COM AppWizard.

2. Select Dynamic Link Library (DLL) as the Server Type and accept the remaining
  defaults.

3. On the Insert menu, click New ATL Object.

4. Select controls from the category list on the left.

5. Select Full Control.

6. Give the control a name and accept the remaining defaults.

7. Build the control.

8. Start Access97 and open a database.

9. Insert a new form.

10. Insert the control and place it on the form.

11. Save the form and close it.

12. Attempt to re-open the form, and note that you receive a message box stating
  "There is no object in this control."

REFERENCES
==========

For additional information, please click the article number below to view the
article in the Microsoft Knowledge Base:

  Q177105 ACC97: "No Object in This Control" Inserting Web Browser

Additional query words:

======================================================================
Keywords          : kbnokeyword kbAccess97 kbATL210 kbCOMt kbContainer kbCtrlCreate kbVC500 kbVC600 kbATL300 kbDSupport kbGrpDSMFCATL 
Technology        : kbVCsearch kbAudDeveloper kbAccessSearch kbAccess97 kbAccess97Search kbVC500 kbVC600 kbVC32bitSearch kbVCNET kbVC500Search
Version           : :5.0,6.0
Issue type        : kbprb

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