BUG: DDX_ and DDP_ Functions Don't Work for ComboBoxEx in COlePropertyPage

• The Microsoft Foundation Classes (MFC), included with:
  • Microsoft Visual C++, 32-bit Editions, versions 5.0, 6.0

SYMPTOMS

If the user has an extended combo box in a COlePropertyPage class, and uses the DDX_ functions and the DDP_ functions to set a control property with the extended combo box control, the property is not persisted when the selection is changed in the extended combo box.

CAUSE

The problem is in the COlePropertyPage::OnCommand function in the Ctlppg.cpp file. This function calls the SetControlStatus and SetModifiedFlag functions in response to a CBN_EDITCHANGE notification message, but only if the class name of the window is "COMBOBOX".

The COlePropertyPage::OnCommand function also needs to call the SetControlStatus and SetModifiedFlag functions in response to a CBN_EDITCHANGE notification message for the class name "COMBOBOXEX32".

RESOLUTION

To work around this problem, you can handle the CBN_EDITCHANGE notification and call SetControlStatus and SetModifiedFlag. The code for the message map and the handler function should resemble the following:

BEGIN_MESSAGE_MAP(CTestPropPage, COlePropertyPage)
	//{{AFX_MSG_MAP(CTestPropPage)
	ON_CBN_EDITCHANGE(IDC_COMBOBOXEX1, OnEditchangeComboboxex1)
	//}}AFX_MSG_MAP
END_MESSAGE_MAP()

void CTestPropPage::OnEditchangeComboboxex1() 
{
	SetControlStatus(IDC_COMBOBOXEX1, TRUE);
	SetModifiedFlag ();
}
 

STATUS

Microsoft has confirmed this to be a bug in the Microsoft products listed at the beginning of this article.

MORE INFORMATION

Steps to Reproduce Behavior

1. Use MFC ActiveX ControlWizard to generate an ActiveX control project called Test.



2. Add a custom property called MyProperty, the type is CString.



3. Add an extended combo box to the control property page resource.



4. Associate the string value of the combo box with MyProperty. The following entries should be added to the DoDataExchange function if you define m_strMyProperty as the variable name:




DDP_CBString(pDX, IDC_COMBOBOXEX1, m_strMyProperty, _T("MyProperty") );
DDX_CBString(pDX, IDC_COMBOBOXEX1, m_strMyProperty); 

5. Build the ActiveX control.



6. Test the ActiveX control in the ActiveX Control Test Container. You should find that the property is not being persisted.

Additional query words: DDP_CBString DDX_CBString DoDataExchange SetControlStatus SetModifiedFlag

Keywords : kbComboBox kbCOMt kbDlg kbMFC kbPersistSt kbPropSheet kbVC500bug kbVC600bug kbDSupport kbGrpMFCATL
Version : winnt:5.0,6.0
Platform : winnt
Issue type : kbbug