/**
  * save folderstate (aka: remember that we have sent the folder to the client)
  *
  * @param string $_class the class from the xml
  * @param string $_folderId the Tine 2.0 id of the folder
  */
 protected function _addFolderState($_class, $_folderId)
 {
     $folderState = new ActiveSync_Model_FolderState(array('device_id' => $this->_device->getId(), 'class' => $_class, 'folderid' => $_folderId, 'creation_time' => $this->_syncTimeStamp));
     /**
      * if the entry got added earlier, and there was an error, the entry gets added again
      * @todo it's better to wrap the whole process into a transation
      */
     try {
         $this->_folderStateBackend->create($folderState);
     } catch (Zend_Db_Statement_Exception $e) {
         $this->_deleteFolderState($_class, $_folderId);
         $this->_folderStateBackend->create($folderState);
     }
 }