Radio Buttons in MFC (Visual Studio 2008 / C++)

This is a quick and dirty description of how to use radio buttons in MFC, written because I could not find this information in a single place on the web.

In the dialog editor:

• Create a new group with the group box control and set a meaningful caption.
• Add radio button controls inside the group.
• The radio buttons must have ascending tab order.
• The first radio button (in tab order) must have the property "Group" set to True.
• All other radio buttons must have the property "Group" set to False.

It should look similar to this:

In the header file defining the dialog class:

• Add a member variable of type int that will store which radio button is selected (none: -1, first: 0, second: 1, and so on).
  Example:

  int m_nLEDType;

In the CPP file implementing the dialog class:

• In the constructor, initialize the member variable (with 0)
  Example:

  CDialogConfig::CDialogConfig(CMainFrame* pMainFrame) : 
  	CDialog(CDialogConfig::IDD, pMainFrame), m_nLEDType(0)

• In DoDataExchange, add a call to DDX_Radio similar to the following (where IDC_RADIO_LEDTYPE1 is the ID of the first radio button):

  DDX_Radio(pDX, IDC_RADIO_LEDTYPE1, m_nLEDType);

When you want to read which radio button is selected:

• Call UpdateData with a parameter of true (indicates reading):

  UpdateData (TRUE);

• After UpdateData has been called, the member variable (m_nLEDType in this example) has the current state of the buttons.

When you want to select one of the buttons programmatically:

• Set the member variable to the correct value (none selected: -1, first button selected: 0, second button selected: 1, and so on)
• Call UpdateData with a parameter of false (indicates writing):

  UpdateData (FALSE);