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Q128894: PRB: C2189 and C2857 Errors When AFXDB.H Used for UNICODE

Article: Q128894
Product(s): Microsoft C Compiler
Version(s): winnt:
Operating System(s): 
Keyword(s): kbwizard kbDatabase kbDLL kbMFC kbODBC kbVC kbprb
Last Modified: 29-JUL-2001

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The information in this article applies to:

- The Microsoft Foundation Classes (MFC), included with:
   - *EDITOR Please do not choose this product*Microsoft Visual C++ 32-bit Edition* use 241, 265, 225, versions 2.0, 2.1 
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SYMPTOMS
========

When attempting to build an AppWizard-generated DLL or EXE with ODBC support,
two compiler errors are generated when STDAFX.CPP is compiled :

  <Path>\msvc20\mfc\include\afxdb.h(15): error C2189: #error: Database
  classes not supported in this library variant.

  <Path>\stdafx.cpp(7): error C2857: '#include' statement specified with
  the /Ycstdafx.h command-line option was not found in the source file.

CAUSE
=====

The project settings for the DLL or EXE have been changed so that _UNICODE is
defined, instead of _MBCS.

When using AppWizard to generate a DLL or an EXE with ODBC support, AppWizard
automatically adds the following to the STDAFX.H file it generates:

     #include <afxdb.h>

However, ODBC does not support Unicode, so MFC produces a compilation error
whenever an attempt is made to build a Unicode application or DLL that includes
the MFC database classes header file (AFXDB.H).

RESOLUTION
==========

1. If you are not using the MFC database classes, remove the following line from
  your STDAFX.H file:

     #include <afxdb.h>

2. If you are using the MFC database classes, do not build a Unicode variant of
  your DLL or EXE. The database classes rely on ODBC, which does not support
  Unicode.

STATUS
======

This behavior is by design.

Additional query words: 2.00 2.10 dll unicode database

======================================================================
Keywords          : kbwizard kbDatabase kbDLL kbMFC kbODBC kbVC kbprb 
Technology        : kbAudDeveloper kbMFC
Version           : winnt:
Issue type        : kbprb

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