Interesting!! - Inheritance problem

[Sanjeet Joshi]

THE SOULUTION IN THE REPLY GIVEN TO THIS MESSAGE BY ANONYM DID NOT WORK !!!
HI,

I am writting a DLL of custom controls. i.e. some additional features added to existing windows controls. So I have written this CMyListCtrl class that enhances CListCtrl MFC class. The class is exported as following :

class __declspec(dllexport) CMyListCtrl : public CListCtrl
{
//class body goes here
};

The dll is created without any problems.

I can use this dll and the control class in other applications, and make use of CMyListCtrl where ever I can. There is no problem in it.

The problem starts when I try to inherit another class from CMyListCtrl in some other application.

For e.g. I create another project import the dll of custom controls.
Then I write a class as following:

class CAnotherListCtrl : public CMyListCtrl
{
//class body.
};

When I compile the application linker gives me following error :

TestListCtrl.obj : error LNK2001: unresolved external symbol "protected: static struct AFX_MSGMAP const CMyListCtrl::messageMap" (?messageMap@CMyListCtrl@@1UAFX_MSGMAP@@B)
Debug/DLLUseTest.exe : fatal error LNK1120: 1 unresolved externals

I suspected it is because of the DECLARE_MESSAGE_MAP() or BEGIN_MESSAGE_MAP() macros. So I changed the BEGIN_MESSAGE_MAP macro from :

BEGIN_MESSAGE_MAP(CAnotherListCtrl, CMyListCtrl)

to

BEGIN_MESSAGE_MAP(CAnotherListCtrl, CListCtrl)

and the error was gone. But obviously all the message handling in CMyListCtrl was gone.

Does anybody know whats happening ? So the basic question would be 'How do we write a library of Custom controls (inherited from MFC) that can be used to further define new clasees ?'

Is this because something is not getting exported properly ?

Please feedback

Sanjeet.

You must select project type of MFC Extension DLL. This adds the additional macros to that if you declare your class as AFX_EXT_CLASS it will have it's message maps exported as well.

[Sanjeet Joshi]

No it did not work.

I am still getting the same error!

This is what I did :

I created a new project with type MFC Extention DLL.

Then I declared my class as AFX_EXT_CLASS (this macro is nothing but
__declspec(dllexport) that I already had otherwise my class members wouldn't have been exported in the first place.) But anyway I changed it to AFX_EXT_CLASS. Then I used the class in other application.
Still the error remains.

What could be going wrong ?

Cheers
Sanjeet