public function AddForm() { $form = parent::AddForm(); $fields = $form->Fields(); $fields->push(new HiddenField('Parent', null, true)); // Enforce a parent mode of "child" to correctly read the "allowed children". $fields->dataFieldByName('ParentModeField')->setValue('child'); $fields->insertAfter($parent = new TreeDropdownField('ParentID', '', 'SiteTree', 'ID', 'TreeTitle'), 'ParentModeField'); $parentID = $this->request->getVar('ParentID'); $parentID = $parentID ? $parentID : Multisites::inst()->getCurrentSiteId(); $parent->setForm($form); $parent->setValue((int) $parentID); $form->setValidator(new RequiredFields('ParentID')); return $form; }