protected function renderDropdown()
    {
        $lines = [];
        $lines[] = $this->encodeText ? Html::encode($this->text) : $this->text;
        if ($this->icon && is_string($this->icon)) {
            $lines[] = $this->icon;
        }
        $lines[] = $this->renderItems($this->items, $this->options, $this->displaySearchInput);
        return Html::tag('div', implode("\n", $lines), $this->options);
    }