public function Delete($ActivityID = '', $TransientKey = '') {
      $Session = Gdn::Session();
      if (!$Session->ValidateTransientKey($TransientKey))
         throw PermissionException();
      
      if (!is_numeric($ActivityID))
         throw Gdn_UserException('Invalid activity ID');
      
      
      $HasPermission = $Session->CheckPermission('Garden.Activity.Delete');
      if (!$HasPermission) {
         $Activity = $this->ActivityModel->GetID($ActivityID);
         if (!$Activity)
            throw NotFoundException('Activity');
         $HasPermission = $Activity['InsertUserID'] == $Session->UserID;
      }
      if (!$HasPermission)
         throw PermissionException();

      $this->ActivityModel->Delete($ActivityID);
      
      if ($this->_DeliveryType === DELIVERY_TYPE_ALL)
         Redirect(GetIncomingValue('Target', $this->SelfUrl));
      
      // Still here? Getting a 404.
      $this->ControllerName = 'Home';
      $this->View = 'FileNotFound';
      $this->Render();
   }