private static void HandleSelectionChanged(object sender, RoutedEventArgs e)
{
var mathBox = (MathBox)sender;
if (Equals(e.OriginalSource, sender))
{
TextPointer caret = mathBox.CaretPosition;
InlineUIContainer forwardUiElement = caret.GetAdjacentUIContainer(LogicalDirection.Forward);
InlineUIContainer backwardUiElement = caret.GetAdjacentUIContainer(LogicalDirection.Backward);
mathBox.ForwardUiElement = forwardUiElement;
mathBox.BackwardUiElement = backwardUiElement;
}
}