How to make Silverlight Grid to allow only one Checkbox to select.

CheckBox previousCheckBox = null;
        private void chkPerson_Click(object sender, RoutedEventArgs e)
        {
            if(previousCheckBox!=null)
            {
                previousCheckBox.IsChecked = false;
            }

            CheckBox currentCheckBox = sender as CheckBox;
            previousCheckBox = currentCheckBox;
        }

        private void chkPerson_Unchecked(object sender, RoutedEventArgs e)
        {
            previousCheckBox = null;
        }