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I have developed a base class to assist with multi-threaded database access that I would like to make use of in a huge (50+) number of dialogs. The way that makes the most sense is to have my class inherit from CWnd and to then have a number of different control class's, such as CListCtrl, CComboBox, CListBox, etc inherit from my class. The only way I can think of doing this is to rebuild the MFC DLL's after modifying the source. This sounds like to daunting a task, even for the likes of me  . Does anyone else have a tip or suggestion to try instead. Thanks and I can elaborate more if you have questions.
Chris
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Multiple inheritance is out of question? You could put DB-related functionality in separate class and create CEditDB, CListCtrlDB, CComboBoxDB etc.
Tomasz Sowinski -- http://www.shooltz.com.pl
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Thanks Tomasz. I think going the multiple inheritance route is probably the best. My only knock against it is that I end up having to duplicate a number of methods in the controls that are really window specific. For example, I want to handle the OnDestroy() and cleanup the base class. Each control will need to handle the message and run the same code. If I could get my class into the hierarchy between the CWnd class and CWhateverControl class, then I only have to write the OnDestroy handler once. That's really what I was trying to avoid. Thanks for the suggestion, it will probably be the way that I end up going.
Chris
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> If I could get my class into the hierarchy between the CWnd
> class and CWhateverControl class, then I only have to write
> the OnDestroy handler once.
You can check Paul DiLascia's CMsgHook class, described in March 1997 issue of MSJ ("More Fun With MFC: DIBs, Palettes, Subclassing and a Gamut of Goodies, Part II"). This class isn't derived from CWnd and makes Windows message processing possible outside of CWnd hierarchy. Even if it doesn't solve your problem, it's very good reading - DiLascia has its own unique, funny style.
The article should be in the 'Periodicals' section of MSDN installed on your HD --and-- it's available at msdn.microsoft.com.
Tomasz Sowinski -- http://www.shooltz.com.pl
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I enjoy his articles too. They have that "I've been through the wars" kinda feel to them 
Thanks again.
Chris
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What does your base class represent?
If you want the controls to inherit from your class, then Why do you need Multithreaded-database access per control??
Your classes should represent entities like record and recordset. And then you need RFX mechanism for the controls!
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It represents a window that when created or subclassed, will start a thread that performs the database access. When properly implemented, the dialog and controls can be created much faster, providing an application that is responsive. Put together a dialog with 4 listboxes, 8 comboboxes, 1 list control and if you try to populate the data in these controls during OnInitDialog(), all it takes is for just one of the controls to have to load a large number of records, eg. a couple of thousand, and your user has to sit and wait. But if the OnCreate or PreSubclass method is used to start a thread that populates the data, then the dialog appears much quicker and is more responsive.
Chris
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Sounds Cool! But why don't you create base classes like CSQLQuery, CRecordset
and then derive CDialogRecordset from that. You can make your CDialogRecordset class so that it would create a second thread and does the work there... and it uploads the controls automatically!
You also need to define some MACROS to MAP dialog controls to certain fields!
Does this work?
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I maybe totally off the mark here, but have you considered making your class a template class?
<br />
template <typename T><br />
class CMTDBWnd : public T<br />
{<br />
};<br />
and then use it like so...
CMTDBWnd<CListCtrl> m_listCtrl;
HTH
Jignesh
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You've probably given me a pretty good reason to dig up a tutorial on building templates 
I've only used templates minimally in the past, but this seems like an idea to persue.
Thanks for the suggestion.
Chris
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I am getting the following linkage problem to occur when building. MSDN says they have a solution but
I can't seem to make the solution work.
mfcs42d.lib(dllmodul.obj) : error LNK2005: _DllMain@12 already defined in CreateCharacterCls.obj
mfcs42d.lib(dllmodul.obj) : error LNK2005: __pRawDllMain already defined in CreateCharacterCls.obj
What I try is placing mfcs42d.lib in the Object/library module box under links under project settings, which looked to be what microsoft was trying to tell me. (I also tried placing in under libraries to ignore since that was also mentioned. Perhaps I using the wrong libraries.)
Does anyone know the real solution around this. Either I'm reading the microsoft solution wrong, or it's not descriptive enough on the solution.
Thanks!
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It looks like the simpler solution (from MSDN) would be:
"When using MFC libraries, you must make sure they are linked before the CRT library. This can be done by ensuring every file in your project includes ..\Msdev\Mfc\Include\Afx.h first, either directly [#include <afx.h>] or indirectly [#include <Stdafx.h>]. The Afx.h include file forces the correct order of the libraries, by using the #pragma comment [lib,"<libname>"] directive. [from PRB: LNK2005 Errors When Link C Run-Time Libs Before MFC Libs ]
Just making sure all your .cpp files include stdafx.h might do it.
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Not quite. Every cpp file already had a Stdafx.h included.
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Well, guess we're on the same help page anyway - would be interesting to look at the output if you type /verbose:lib into the project options on the link tab.
Also, note that when you put the lib in the modules list it should be at the beginning. (I know, it says that - just a double check!) Still, the verbose info should be helpful.
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Linking...
Searching Libraries
Searching C:\Program Files\Microsoft Visual Studio\VC98\MFC\LIB\mfcs42d.lib:
mfcs42d.lib(dllmodul.obj) : error LNK2005: _DllMain@12 already defined in CreateCharacterCls.obj
mfcs42d.lib(dllmodul.obj) : error LNK2005: __pRawDllMain already defined in CreateCharacterCls.obj
Searching \Program Files\Microsoft Visual Studio\MyProjects\RoleMaker\CharacterCls\Debug\CharacterCls.lib:
Searching \Program Files\Microsoft Visual Studio\MyProjects\RoleMaker\DatabaseRoutinesCls\Debug\DatabaseRoutinesCls.lib:
Searching \Program Files\Microsoft Visual Studio\MyProjects\RoleMaker\CustomCtrlsCls\Debug\CustomCtrlsCls.lib:
Searching C:\Program Files\Microsoft Visual Studio\VC98\MFC\LIB\mfc42d.lib:
Searching C:\Program Files\Microsoft Visual Studio\VC98\LIB\msvcrtd.lib:
Searching C:\Program Files\Microsoft Visual Studio\VC98\LIB\kernel32.lib:
Searching C:\Program Files\Microsoft Visual Studio\VC98\LIB\user32.lib:
Searching C:\Program Files\Microsoft Visual Studio\VC98\LIB\gdi32.lib:
Searching C:\Program Files\Microsoft Visual Studio\VC98\LIB\comdlg32.lib:
Searching C:\Program Files\Microsoft Visual Studio\VC98\LIB\winspool.lib:
Searching C:\Program Files\Microsoft Visual Studio\VC98\LIB\advapi32.lib:
Searching C:\Program Files\Microsoft Visual Studio\VC98\LIB\shell32.lib:
Searching C:\Program Files\Microsoft Visual Studio\VC98\LIB\comctl32.lib:
Searching C:\Program Files\Microsoft Visual Studio\VC98\LIB\uuid.lib:
Searching C:\Program Files\Microsoft Visual Studio\VC98\MFC\LIB\mfco42d.lib:
Searching C:\Program Files\Microsoft Visual Studio\VC98\LIB\oledlg.lib:
Searching C:\Program Files\Microsoft Visual Studio\VC98\LIB\ole32.lib:
Searching C:\Program Files\Microsoft Visual Studio\VC98\LIB\olepro32.lib:
Searching C:\Program Files\Microsoft Visual Studio\VC98\LIB\oleaut32.lib:
Searching C:\Program Files\Microsoft Visual Studio\VC98\LIB\urlmon.lib:
Searching C:\Program Files\Microsoft Visual Studio\VC98\MFC\LIB\mfcd42d.lib:
Searching C:\Program Files\Microsoft Visual Studio\VC98\LIB\odbc32.lib:
Searching C:\Program Files\Microsoft Visual Studio\VC98\LIB\odbccp32.lib:
Searching C:\Program Files\Microsoft Visual Studio\VC98\LIB\daouuid.lib:
Searching C:\Program Files\Microsoft Visual Studio\VC98\MFC\LIB\mfcn42d.lib:
Searching C:\Program Files\Microsoft Visual Studio\VC98\LIB\wsock32.lib:
Searching C:\Program Files\Microsoft Visual Studio\VC98\LIB\OLDNAMES.lib:
Searching C:\Program Files\Microsoft Visual Studio\VC98\MFC\LIB\mfcs42d.lib:
Searching \Program Files\Microsoft Visual Studio\MyProjects\RoleMaker\CharacterCls\Debug\CharacterCls.lib:
Searching \Program Files\Microsoft Visual Studio\MyProjects\RoleMaker\DatabaseRoutinesCls\Debug\DatabaseRoutinesCls.lib:
Searching \Program Files\Microsoft Visual Studio\MyProjects\RoleMaker\CustomCtrlsCls\Debug\CustomCtrlsCls.lib:
Searching C:\Program Files\Microsoft Visual Studio\VC98\MFC\LIB\mfc42d.lib:
Searching C:\Program Files\Microsoft Visual Studio\VC98\LIB\msvcrtd.lib:
Searching C:\Program Files\Microsoft Visual Studio\VC98\LIB\kernel32.lib:
Searching C:\Program Files\Microsoft Visual Studio\VC98\LIB\user32.lib:
Searching C:\Program Files\Microsoft Visual Studio\VC98\LIB\gdi32.lib:
Searching C:\Program Files\Microsoft Visual Studio\VC98\LIB\comdlg32.lib:
Searching C:\Program Files\Microsoft Visual Studio\VC98\LIB\winspool.lib:
Searching C:\Program Files\Microsoft Visual Studio\VC98\LIB\advapi32.lib:
Searching C:\Program Files\Microsoft Visual Studio\VC98\LIB\shell32.lib:
Searching C:\Program Files\Microsoft Visual Studio\VC98\LIB\comctl32.lib:
Searching C:\Program Files\Microsoft Visual Studio\VC98\LIB\uuid.lib:
Searching C:\Program Files\Microsoft Visual Studio\VC98\MFC\LIB\mfco42d.lib:
Searching C:\Program Files\Microsoft Visual Studio\VC98\LIB\oledlg.lib:
Searching C:\Program Files\Microsoft Visual Studio\VC98\LIB\ole32.lib:
Searching C:\Program Files\Microsoft Visual Studio\VC98\LIB\olepro32.lib:
Searching C:\Program Files\Microsoft Visual Studio\VC98\LIB\oleaut32.lib:
Searching C:\Program Files\Microsoft Visual Studio\VC98\LIB\urlmon.lib:
Done Searching Libraries
mfcs42d.lib(dllmodul.obj) : warning LNK4006: _DllMain@12 already defined in CreateCharacterCls.obj; second definition ignored
mfcs42d.lib(dllmodul.obj) : warning LNK4006: __pRawDllMain already defined in CreateCharacterCls.obj; second definition ignored
Creating library Debug/CreateCharacterCls.lib and object Debug/CreateCharacterCls.exp
Searching Libraries
Searching C:\Program Files\Microsoft Visual Studio\VC98\MFC\LIB\mfcs42d.lib:
Searching \Program Files\Microsoft Visual Studio\MyProjects\RoleMaker\CharacterCls\Debug\CharacterCls.lib:
Searching \Program Files\Microsoft Visual Studio\MyProjects\RoleMaker\DatabaseRoutinesCls\Debug\DatabaseRoutinesCls.lib:
Searching \Program Files\Microsoft Visual Studio\MyProjects\RoleMaker\CustomCtrlsCls\Debug\CustomCtrlsCls.lib:
Searching C:\Program Files\Microsoft Visual Studio\VC98\MFC\LIB\mfc42d.lib:
Searching C:\Program Files\Microsoft Visual Studio\VC98\LIB\msvcrtd.lib:
Searching C:\Program Files\Microsoft Visual Studio\VC98\LIB\kernel32.lib:
Searching C:\Program Files\Microsoft Visual Studio\VC98\LIB\user32.lib:
Searching C:\Program Files\Microsoft Visual Studio\VC98\LIB\gdi32.lib:
Searching C:\Program Files\Microsoft Visual Studio\VC98\LIB\comdlg32.lib:
Searching C:\Program Files\Microsoft Visual Studio\VC98\LIB\winspool.lib:
Searching C:\Program Files\Microsoft Visual Studio\VC98\LIB\advapi32.lib:
Searching C:\Program Files\Microsoft Visual Studio\VC98\LIB\shell32.lib:
Searching C:\Program Files\Microsoft Visual Studio\VC98\LIB\comctl32.lib:
Searching C:\Program Files\Microsoft Visual Studio\VC98\LIB\uuid.lib:
Searching C:\Program Files\Microsoft Visual Studio\VC98\MFC\LIB\mfco42d.lib:
Searching C:\Program Files\Microsoft Visual Studio\VC98\LIB\oledlg.lib:
Searching C:\Program Files\Microsoft Visual Studio\VC98\LIB\ole32.lib:
Searching C:\Program Files\Microsoft Visual Studio\VC98\LIB\olepro32.lib:
Searching C:\Program Files\Microsoft Visual Studio\VC98\LIB\oleaut32.lib:
Searching C:\Program Files\Microsoft Visual Studio\VC98\LIB\urlmon.lib:
Searching C:\Program Files\Microsoft Visual Studio\VC98\MFC\LIB\mfcd42d.lib:
Searching C:\Program Files\Microsoft Visual Studio\VC98\LIB\odbc32.lib:
Searching C:\Program Files\Microsoft Visual Studio\VC98\LIB\odbccp32.lib:
Searching C:\Program Files\Microsoft Visual Studio\VC98\LIB\daouuid.lib:
Searching C:\Program Files\Microsoft Visual Studio\VC98\MFC\LIB\mfcn42d.lib:
Searching C:\Program Files\Microsoft Visual Studio\VC98\LIB\wsock32.lib:
Searching C:\Program Files\Microsoft Visual Studio\VC98\LIB\OLDNAMES.lib:
Done Searching Libraries
C:/Windows/System/CreateCharacterCls.dll : fatal error LNK1169: one or more multiply defined symbols found
Error executing link.exe.
CreateCharacterCls.dll - 3 error(s), 22 warning(s)
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The above response is from me. It says anonymous. I sent this without signing on. Just clearing any confusion. 
"Why are we hiding from the police, Daddy?"
"We use VI, son. They use Emacs."
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Are you building an MFC extension DLL? Is it using AFX_MANAGE_STATE(AfxGetStaticModuleState( ) )? There's an article [Q161589] that describes this as an error in the docs that can lead to this link problem.
The output you posted was not what I expected - I thought the error would happen later and point to an obj file that wasn't bringing in the afx stuff.
BTW sometimes you can /force linkage in this type of scenario (Force file output on the Link / customize tab) but do this only for an experiment.
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The tech docs referenced here fixed the problem.
FYI. using FORCE will help with the problem but will reak havoc during run time. I can't remember the specifics, but it causes problems with dialog based DLLs.
Thanks for the insight!
Chris
"Why are we hiding from the police, Daddy?"
"We use VI, son. They use Emacs."
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Thank you, please continue !
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CFile::Read( void* lpBuf, UINT nCount );
CFile::Read returns the number of bytes transferred to the buffer. If the value returned is less than nCount the end of file was reached.
Cheers!!!
Carlos Antollini.
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I can display that 0-10 numbers....but then get a memory error message.....what's wrong?
int *pPtr;
pPtr = new int;
CString a;
for (int i=0; i<=10; i++)
{
*(pPtr+i) = i;
Display Pointer here.......
}
delete pPtr;
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If you have only 10 items in the array, use ; i < 10 ; in the loop (0 to 9 are valid indices). A common gotcha, to be sure.
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