public function AddForm() {
		$classes = ClassInfo::subclassesFor(self::$tree_class);
		array_shift($classes);

		foreach ($classes as $key => $class) {
			if (!singleton($class)->canCreate())
				unset($classes[$key]);
			$classes[$key] = FormField::name_to_label($class);
		}

		$fields = new FieldList(
			new HiddenField("ParentID"),
			new HiddenField("Locale", 'Locale', i18n::get_locale()),
			$type = new DropdownField("ProviderType", "", $classes)
		);
		$type->setAttribute('style', 'width:150px');

		$actions = new FieldList(
			FormAction::create("addprovider", _t('ExternalContent.CREATE', "Create"))
				->addExtraClass('ss-ui-action-constructive')->setAttribute('data-icon', 'accept')
				->setUseButtonTag(true)
		);

		$form = new Form($this, "AddForm", $fields, $actions);

		$form->addExtraClass('cms-edit-form ' . $this->BaseCSSClasses());
		$this->extend('updateEditForm', $form);

		return $form;
	}