Entity::getUserGridColumnIds

protected function getUserGridColumnIds()
{
	$result = $this->gridConfig->GetVisibleColumns();
	if (empty($result))
	{
		$oldOptions = CUserOptions::GetOption('list', $this->getGridId(), []);
		if (!empty($oldOptions['columns']))
		{
			$oldGridColumns = [];
			$rawColumns = explode(',', $oldOptions['columns']);
			foreach ($rawColumns as $id)
			{
				$id = trim($id);
				if ($id !== '')
					$oldGridColumns[] = $id;
			}
			unset($id, $rawColumns);
			if (!empty($oldGridColumns))
				$result = $oldGridColumns;
			unset($oldGridColumns);
		}
		unset($oldOptions);

		if (!empty($result))
			$this->gridConfig->SetVisibleColumns($result);
	}
	if (!empty($result) && !in_array('ID', $result))
		array_unshift($result, 'ID');
	return $result;
}