Prado\Web\UI\WebControls\TRequiredFieldValidator::validateListControl PHP Method

    private function validateListControl($control)
    {
        $initial = trim($this->getInitialValue());
        $count = 0;
        foreach ($control->getItems() as $item) {
            if ($item->getSelected() && $item->getValue() != $initial) {
                $count++;
            }
        }
        return $count > 0;
    }