GroupBox

Traditionally, a group of mutually exclusive radio buttons are children of a group box, which is a control with a simple outline border and a text heading. In the Windows Presentation Foundation, this is the GroupBox control, which is one of three classes that descend from HeaderedContentControl:

Control
---ContentControl
------HeaderedContentControl
---------Expander
---------GroupBox
---------TabItem

Because HeaderedContentControl derives from ContentControl, these controls have a Content property. The controls also have a Header property, which (like Content) is of type object. GroupBox adds nothing to HeaderedContentControl. Use the Header property to set the heading at the top of the GroupBox. Although this heading is customarily text, you can really make it whatever you want. Use Content for the interior of the GroupBox. You'll probably want to put a StackPanel in there.

//IN WINDOWS CONSTRUCTOR
{
Title = "Tune the Radio";
    SizeToContent = SizeToContent.WindowandHeight;

    GroupBox group = new GroupBox();
    group.Header = "Window Style";
    group.Margin = new Thickness(96);
    group.Padding = new Thickness(5);
    Content = group;
//
    StackPanel stack = new StackPanel();
    group.Content = stack;
//
    stack.Children.Add( CreateRadioButton("No border or caption",
                          WindowStyle.None));
    stack.Children.Add( CreateRadioButton("Single-border window",
                          WindowStyle.SingleBorderWindow));
    stack.Children.Add(CreateRadioButton("3D-border window",
                          WindowStyle.ThreeDBorderWindow));
    stack.Children.Add(      CreateRadioButton("Tool window",
                          WindowStyle.ToolWindow));
//
    AddHandler(RadioButton.CheckedEvent, new RoutedEventHandler(
RadioOnChecked));

}//End THE CONSTRUCTOR
RadioButton CreateRadioButton(string strText, WindowStyle winstyle)
{
    RadioButton radio = new RadioButton();
    radio.Content = strText;
    radio.Tag = winstyle;
    radio.Margin = new Thickness(5);
    radio.IsChecked = (winstyle ==WindowStyle);

    return radio;
}
//
void RadioOnChecked(object sender,RoutedEventArgs args)
{
    RadioButton radio = args.Source as RadioButton;
    WindowStyle = (WindowStyle)radio.Tag;
}

The checking and unchecking of sibling radio buttons happens automatically from either the mouse or keyboard. When you're using the keyboard, the cursor movement keys change the input focus among the sibling radio buttons. The space bar checks the currently focused button. All the program needs to do is monitor which button is being checked. (Some programs might also need to know when a button is losing its check mark.) It is usually most convenient to use the same event handler for sibling radio buttons. When writing code for the event handler, keep in mind that the IsChecked property has already been set.

It could be that you have a bunch of sibling radio buttons that comprise two or more mutually exclusive groups. To distinguish between these groups, use the GroupName property defined by RadioButton. Set GroupName to a unique string for each group of mutually exclusive buttons, and the multiple groups will be automatically checked and unchecked correctly. You can use the same GroupName property in your event handler to determine which group of buttons is affected.