Knowledge Base

PRB: CWnd::m_nMsgDragList Not Exported by the MFC DLL

Article ID: 189382

Article Last Modified on 11/21/2006

Microsoft Foundation Class Library 4.2, when used with:
- Microsoft Visual C++ 5.0 Enterprise Edition
- Microsoft Visual C++ 5.0 Professional Edition

This article was previously published under Q189382

SYMPTOMS

When you use the protected CWnd member m_nMsgDragList in an application or DLL that is linked to the MFC shared DLL, a LNK2001 unresolved external error occurs.

This error does not occur when you link to the static MFC library.

CAUSE

CWnd::m_nMsgDragList is not exported from the MFC DLL.

RESOLUTION

To workaround this problem, call RegisterWindowMessage with the DRAGLISTMSGSTRING message and use the value returned instead of CWnd::m_nMsgDragList. For example:

   UINT nMsgDragList = ::RegisterWindowMessage(DRAGLISTMSGSTRING);

STATUS

This behavior is by design.

MORE INFORMATION

CWnd::m_nMsgDragList is an undocumented member of the CWnd class and is subject to change. The most common use of CWnd::m_nMsgDragList occurs when you override OnChildNotify in a CWnd derived class.

Keywords: kbarchitecture kbdll kbprb KB189382