Knowledge Base

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

Article ID: 128894

Article Last Modified on 11/21/2006

Microsoft Foundation Class Library 4.2, when used with:
- Microsoft Visual C++ 2.0 Professional Edition
- Microsoft Visual C++ 2.1

This article was previously published under Q128894

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

If you are not using the MFC database classes, remove the following line from your STDAFX.H file:
```
   #include <afxdb.h>
						
```
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: kbdatabase kbdll kbprb kbwizard KB128894