Q133307: HOWTO: How to Detect If a CFormView Has Changed

Article: Q133307
Product(s): Microsoft C Compiler
Version(s): winnt:2.0,2.1,2.2,4.0,4.1
Operating System(s): 
Keyword(s): kbDocView kbMFC kbVC kbVC100 kbVC200 kbVC400 kbGrpDSMFCATL kbNoUpdate
Last Modified: 06-MAY-2001

-------------------------------------------------------------------------------
The information in this article applies to:

- The Microsoft Foundation Classes (MFC), used with:
   - Microsoft Visual C++ for Windows, 16-bit edition, versions 1.0, 1.5, 1.51, 1.52 
   - Microsoft Visual C++, 32-bit Editions, versions 2.0, 2.1, 2.2, 4.0, 4.1 
-------------------------------------------------------------------------------

SUMMARY
=======

Changes to the controls on a CFormView-derived class are not automatically
detected by the framework. As in any other CView-derived class, it is up to your
view to let the document know when its content has changed.

MORE INFORMATION
================

When the content of a control on a CFormView-derived class has changed, the
document associated with the view should be marked as modified. Doing this
results in MFC popping up a dialog box asking the user if they want to save the
changed file whenever the user tries to either close the application or load a
different document.

To mark a document associated with a CFormView-derived class as modified, add
OnChange handlers for the controls on the view, and call the CDocument class
member function SetModifiedFlag(TRUE). For example, for an edit control, add a
handler for the EN_CHANGE message in the CFormView-derived class, and call
GetDocument()->SetModifiedFlag(TRUE).

The number of controls for which the programmer should provide OnChange handlers
depends on the extent to which the application serializes the UI state of
CFormView. For example, if the current selection of a listbox is serialized,
then a change in the listbox item selection should be considered a change to the
document.

For controls like a group of option buttons, add handlers for the BN_CLICKED
message in the CFormView-derived class, and if the button selection has changed,
call GetDocument()->SetModifiedFlag(TRUE).

Additional query words: kbinf 1.00 1.50 2.00 2.10 2.20 2.50 2.51 2.52 3.0 3.00 3.1 3.10 3.2 3.20 4.00 4.10

======================================================================
Keywords          : kbDocView kbMFC kbVC kbVC100 kbVC200 kbVC400 kbGrpDSMFCATL kbNoUpdate 
Technology        : kbAudDeveloper kbMFC
Version           : winnt:2.0,2.1,2.2,4.0,4.1
Issue type        : kbhowto

=============================================================================

THE INFORMATION PROVIDED IN THE MICROSOFT KNOWLEDGE BASE IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND. MICROSOFT DISCLAIMS ALL WARRANTIES, EITHER EXPRESS OR IMPLIED, INCLUDING THE WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT SHALL MICROSOFT CORPORATION OR ITS SUPPLIERS BE LIABLE FOR ANY DAMAGES WHATSOEVER INCLUDING DIRECT, INDIRECT, INCIDENTAL, CONSEQUENTIAL, LOSS OF BUSINESS PROFITS OR SPECIAL DAMAGES, EVEN IF MICROSOFT CORPORATION OR ITS SUPPLIERS HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. SOME STATES DO NOT ALLOW THE EXCLUSION OR LIMITATION OF LIABILITY FOR CONSEQUENTIAL OR INCIDENTAL DAMAGES SO THE FOREGOING LIMITATION MAY NOT APPLY.

Copyright Microsoft Corporation 1986-2002.