DOCUMENT:Q150122 03-AUG-2001 [visualc] TITLE :PRB: CDaoRecordView Toolbar Buttons Malfunction PRODUCT :Microsoft C Compiler PROD/VER:4.00 4.10 4.20 4.20b 5.00 OPER/SYS: KEYWORDS:kbcode kbusage kbDAOsearch kbDatabase kbMFC kbVC kbVC400 kbVC410 kbVC420 kbVC500 kbVC60 ====================================================================== ------------------------------------------------------------------------------- The information in this article applies to: - The Microsoft Foundation Classes (MFC), included with: - Microsoft Visual C++, 32-bit Editions, versions 4.0, 4.1 - Microsoft Visual C++, 32-bit Enterprise Edition, version 4.2 - Microsoft Visual C++, 32-bit Professional Edition, version 4.2 - Microsoft Visual C++, 32-bit Enterprise Edition, version 4.2b - Microsoft Visual C++, 32-bit Professional Edition, version 4.2b - Microsoft Visual C++, 32-bit Enterprise Edition, version 5.0 - Microsoft Visual C++, 32-bit Professional Edition, version 5.0 - Microsoft Visual C++, 32-bit Enterprise Edition, version 6.0 - Microsoft Visual C++, 32-bit Professional Edition, version 6.0 - Microsoft Visual C++, 32-bit Learning Edition, version 6.0 ------------------------------------------------------------------------------- SYMPTOMS ======== CDaoRecordView depends on an instance of CDaoRecordset to display data. The CDaoRecordView class also needs to stay in synchronization with the current record displayed by the CDaoRecordset instance. Calling the Seek, MoveFirst, MoveNext, or other methods directly on the CDaoRecordset being used by a CDaoRecordView causes the CDaoRecordView to behave incorrectly. CAUSE ===== CDaoRecordView uses four member variables to keep track of bookkeeping information. The first three variables listed below store bookmarks for the first, last, and current record. The fourth variable is used to enable or disable the toolbar buttons corresponding to MoveFirst, MovePrev, MoveNext, and MoveLast. m_varBookmarkCurrent m_varBookmarkFirst m_varBookmarkLast m_nStatus These variables are only maintained when the CDaoRecordView::OnMove method is invoked. This method invokes the CDaoRecordset MoveFirst, MoveNext, MovePrevious, or MoveLast methods, and updates the variables. Only OnMove keeps these variables in synchronization. The following list contains the more common CDaoRecordset methods that change the current record: - Find - Move - Requery - FindFirst - MoveFirst - Seek - FindLast - MoveLast - SetAbsolutePosition - FindNext - MoveNext - SetBookmark - FindPrev - MovePrev - SetPercentPosition When the AddNew method is called, a new record is added to the recordset but the current record bookmark does not change. To change the newly added record to the current record, use the following method: // set the current bookmark to the newly added record m_pSet->SetBookmark(GetLastModifiedBookmark()); NOTE: GetLastModifiedBookmark() needs to be called right after the call to Update() to return the newly added record. Calling it after one of the recordview MoveXXXX functions returns a bookmark to the record that was current prior to the move operation. RESOLUTION ========== After performing a CDaoRecordset method for an instance utilized by CDaoRecordView, reset the CDaoRecordView's bookkeeping variables as shown in the following code: if (!m_pSet->Seek(...)) { if( !m_pSet->IsEOF() ) { m_varBookmarkCurrent = 1L; // <<- re-initialize m_varBookmarkFirst = // <<- the bookmark m_varBookmarkLast = 0L; // <<- member variables! // Enable toolbar buttons m_nStatus |= AFX_DAOVIEW_SCROLL_BACKWARD;// First & Prev buttons m_nStatus |= AFX_DAOVIEW_SCROLL_NEXT; // next toolbar button m_nStatus |= AFX_DAOVIEW_SCROLL_LAST; // last toolbar button } else { // Move to some valid record } } else { // Seek failed - move to a valid record } STATUS ====== This behavior is by design. MORE INFORMATION ================ Steps to Reproduce Behavior --------------------------- 1. Generate a default AppWizard application named SeekTest, and give it the following attributes: - Database View without File Support. - Select a data source, using DAO and a Table recordset type. - Open the Student Registration database (STDREG32.MDB) on the SECTION table. 2. Using the Resource View, add several text boxes to the IDD_SEEKTEST_FORM dialog resource that appears. Use the CTRL-DBLCLK short-cut to bind columns in SECTION to the dialog resource. 3. Add a button to the IDD_SEEKTEST_FORM resource. Using ClassWizard, add the following code: m_pSet->SetCurrentIndex( _T("PrimaryKey") ); COleVariant varCourse ( _T("MATH201"), VT_BSTRT ); COleVariant varSection( _T( "1" ), VT_BSTRT ); if(! m_pSet->Seek( _T( "=" ), &varCourse, &varSection ) ) { // Seek failed - need to move to a valid record m_pSet->MoveFirst(); } UpdateData( FALSE ); 4. Compile, build, and run the program. 5. Click the MoveNext (>) button and then the MovePrevious (<) button to disable the MoveFirst (|<) and MovePrevious (<) toolbar buttons. 6. Click the Seek button. Note that the MoveFirst and MovePrevious buttons are still incorrectly disabled. Adding the code to clear the bookmarks, and resetting the m_nStatus variable corrects the toolbar and prevents other problems. REFERENCES ========== For additional information, please see the following articles in the Microsoft Knowledge Base: Q145686 CDaoRecordView Bookmark Members Invalid After Requery() Q145719 DAOENROL - Can't See Added Records in Windows 95 Additional query words: ====================================================================== Keywords : kbcode kbusage kbDAOsearch kbDatabase kbMFC kbVC kbVC400 kbVC410 kbVC420 kbVC500 kbVC600 Technology : kbAudDeveloper kbMFC Version : 4.00 4.10 4.20 4.20b 5.00 Issue type : kbprb ============================================================================= 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 2001.