private function CalcLevel()
 {
     $this->level = 0;
     if (!$this->isSubLevel || $this->isEmpty) {
         return;
     }
     $parent = $this->naviTree->ParentOf($this->naviItem);
     while ($parent) {
         ++$this->level;
         $parent = $this->naviTree->ParentOf($parent);
     }
 }
 protected function ParentID()
 {
     $parent = $this->tree->ParentOf($this->item);
     return $parent ? $parent->GetID() : '0';
 }