error: Please use the /MD switch for _AFXDLL builds

If your project is an MFC application (.exe) goto the project properties - C/C++ page - Code generation and choose 'Multi-Threaded DLL' for Release configuaration and 'Multi-Threaded-Debug-Dll' for Debug configuration.

That should solve the issue.

Project->Properties, expand "Configuration Properties" on the left, expand "C/C++", select "Code Generation".

On the right side, click the box next to  "Runtime Library" and select "Multithreaded DLL (/MD)" from the combo pulldown.

When I change to this option - it give me this error:

Building MFC application with /MD[d] (CRT dll version) requires MFC shared dll version. Please #define _AFXDLL or do not use /MD[d]

Any ideas?
Thanks,
Mike

What setting to you have in Project->Properties->Configuration Properties->General in the "Use of MFC" box?

It should say "Use MFC in a Shared DLL".

>>>> requires MFC shared dll version
It looks as if your MFC app wanted to use static MFC libraries (that is one of the options you have when you create the app using the wizard). Unfortunately that setting conflicts with some header errors.

Try to define the _AFXDLL in the preprocessor macros (simply add the _AFXDLL to the already defined list separated by ;) at C/C++  - preprocessor

> Try to define the _AFXDLL in the preprocessor macros

Setting the "Use of MFC" setting to "Use MFC in a Shared DLL" does this for you.

Hmmmm..  I think I might be getting somewhere....  I'm now getting a whole bunch of these errors  (having to do with msvcprtd.lib)

Error      77      error LNK2005: "class std::basic_ostream<char,struct std::char_traits<char> > & __cdecl std::operator<<<char,struct std::char_traits<char>,class std::allocator<char> >(class std::basic_ostream<char,struct std::char_traits<char> > &,class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> > const &)" (??$?6DU?$char_traits@D@std@@V?$allocator@D@1@@std@@YAAAV?$basic_ostream@DU?$char_traits@D@std@@@0@AAV10@ABV?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@0@@Z) already defined in gxinterface.lib(CGxGroupe.obj)      msvcprtd.lib      MyProject

Thank you for any further help you can give!  Very appreciated!

What is gxinterface.lib? How is gxinterface.lib built?

Brute force solution, not recommended but can work in a pinch:

Project->Properties->Configuration Properties->Linker->Command Line, add "/FORCE:MULTIPLE" to the Additional options box.

>>>> "/FORCE:MULTIPLE"
The LNK2005 issue often is caused by inconstencies between single-threaded and multi-threaded libraries. In the above case we have different template instantiations and it is good possible that different versions of the STL were used by different libraries. The /FORCE:MULTIPLE could make your app use wrong template instantiations what might lead to unpredictable errors. As wayside said it is not recommended, Hence, don't do it.