PRB: GetCheckedRadioButton() Returns ID Outside Button Group

ID: Q138663

The information in this article applies to:

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

SYMPTOMS

Usually, the intention while using the CWnd::GetCheckedRadioButton() function is to retrieve, from a group of option buttons, the ID of the one that is selected. However, if it is not used correctly, this function may return the ID of a selected button that lies outside a button group.

CAUSE

The CWnd::GetCheckedRadioButton() function takes two arguments:

nIDFirstButton -- the ID of the first option button.
nIDLastButton -- the ID of the last option button in a group.

It returns the ID of the selected option button in a group of option buttons if both the following conditions hold:

The IDs of the option buttons in the group are consecutive

The IDs are in ascending order

If these conditions are not met, the function may either fail (return 0) or return the ID of a control that is not in the option button group.

STATUS

This behavior is by design.

MORE INFORMATION

The GetCheckedRadioButton() function is designed as a counter-part to the CheckRadioButton() Windows API function prototyped here:


     void CheckRadioButton(HWND hwndDlg,
                           int nIDFirstButton,
                           int nIDLastButton,
                           int nIDCheckButton)

This function clears the selection from all buttons with IDs in the range given by nIDFirstButton and nIDLastButton except the one whose ID is given by nIDCheckButton.

The implementation of the CWnd::GetCheckedRadioButton() function works along the same lines. It cycles through each ID in the range given by nIDFirstButton and nIDLastButton querying each to find out which one is in a selected state. It returns as soon as it finds a selected option.

Additional query words: 2.00 1.50 2.50 2.51 2.52 1.52b 3.00 2.10 3.10 2.20 3.20 4.00

Keywords :
Version : winnt:2.0,2.1,2.2,4.0
Platform : winnt
Issue type :