public function GetCount($UserID = '') {
      $this->SQL
         ->Select('a.ActivityID', 'count', 'ActivityCount')
         ->From('Activity a')
         ->Join('ActivityType t', 'a.ActivityTypeID = t.ActivityTypeID');
      
      if ($UserID != '') {
         $this->SQL
            ->BeginWhereGroup()
            ->Where('a.ActivityUserID', $UserID)
            ->OrWhere('a.RegardingUserID', $UserID)
            ->EndWhereGroup();
      }
      
      $Session = Gdn::Session();
      if (!$Session->IsValid() || $Session->UserID != $UserID)
         $this->SQL->Where('t.Public', '1');

      $this->FireEvent('BeforeGetCount');
      return $this->SQL
         ->Get()
         ->FirstRow()
         ->ActivityCount;
   }