public function GetComments($ActivityIDs) {
      $Result = $this->SQL
         ->Select('c.*')
         ->From('ActivityComment c')
         ->WhereIn('c.ActivityID', $ActivityIDs)
         ->OrderBy('c.ActivityID, c.DateInserted')
         ->Get()->ResultArray();
      Gdn::UserModel()->JoinUsers($Result, array('InsertUserID'), array('Join' => array('Name', 'Photo', 'Email')));
      return $Result;
   }