CDavAddressbookBaseLimited::LoadLimitedEntitiesList

protected function LoadLimitedEntitiesList($collectionId, $account, $maxCount, $filter = []);


/**
 * If user save settings, update cTag to that time
 * @param $collectionId
 * @param array $filter
 * @return string getctag property
 */
public function GetCTag($collectionId, $filter = array())
{
	$principalId = $this->groupdav->GetRequest()->GetPrincipal()->Id();
	$lastModifiedAt = MakeTimeStamp($this->CatalogLastModifiedAt($collectionId, $filter));
	$lastSyncSettingsSaveAt = $this->GetLastSyncSettingSaveTimestamp($principalId);
	if ($lastModifiedAt >= $lastSyncSettingsSaveAt)
	{
		return parent::GetCTag($collectionId, $filter);
	}
	else
	{
		return 'BX:' . $lastSyncSettingsSaveAt;
	}
}