private void AssignOwningSearchGroupId(ISearchableEntity entity)
 {
     if (entity.SearchGroupId > 0)
     {
         entity.OwningSearchGroupId = entity.SearchGroupId;
     }
     else
     {
         //Find the corresponding entity that is assigned to its owning search group.
         ISearchableEntity owningItem = SearchableEntities.FirstOrDefault(item => item.Id == entity.Id && item.SearchGroupId > 0);
         if (owningItem != null)
         {
             entity.OwningSearchGroupId = owningItem.SearchGroupId;
         }
     }
 }