RibbonRadioButton.OnMouseLeftButtonDown Method (MouseButtonEventArgs)
Provides class handling for the MouseLeftButtonDown routed event to prevent the control from receiving keyboard focus.
Assembly: System.Windows.Controls.Ribbon (in System.Windows.Controls.Ribbon.dll)
The Ribbon should not take keyboard focus from the application. This method overrides the default behavior and temporarily sets the Focusable property to false, which prevents the control from taking keyboard focus. It then calls the base method.
Available since 4.5