magento2/app/code/Magento/AdminNotification/Controller/Adminhtml/Notification/MassRemove.php

<?php
/**
 * Copyright © Magento, Inc. All rights reserved.
 * See COPYING.txt for license details.
 */
namespace Magento\AdminNotification\Controller\Adminhtml\Notification;

use Magento\AdminNotification\Controller\Adminhtml\Notification;
use Magento\AdminNotification\Model\InboxFactory as InboxModelFactory;
use Magento\Backend\App\Action;
use Magento\Framework\App\Action\HttpPostActionInterface;

/**
 * AdminNotification MassRemove controller
 */
class MassRemove extends Notification implements HttpPostActionInterface
{

    /**
     * Authorization level of a basic admin session
     *
     * @see _isAllowed()
     */
    const ADMIN_RESOURCE = 'Magento_AdminNotification::adminnotification_remove';
    /**
     * @var InboxModelFactory
     */
    private $inboxModelFactory;

    /**
     * @param Action\Context $context
     * @param InboxModelFactory $inboxModelFactory
     */
    public function __construct(Action\Context $context, InboxModelFactory $inboxModelFactory)
    {
        parent::__construct($context);
        $this->inboxModelFactory = $inboxModelFactory;
    }

    /**
     * @inheritdoc
     */
    public function execute()
    {
        $ids = $this->getRequest()->getParam('notification');
        if (!is_array($ids)) {
            $this->messageManager->addErrorMessage(__('Please select messages.'));
        } else {
            try {
                foreach ($ids as $id) {
                    $model = $this->inboxModelFactory->create()->load($id);
                    if ($model->getId()) {
                        $model->setIsRemove(1)->save();
                    }
                }
                $this->messageManager->addSuccessMessage(__('Total of %1 record(s) have been removed.', count($ids)));
            } catch (\Magento\Framework\Exception\LocalizedException $e) {
                $this->messageManager->addErrorMessage($e->getMessage());
            } catch (\Exception $e) {
                $this->messageManager->addExceptionMessage(
                    $e,
                    __("We couldn't remove the messages because of an error.")
                );
            }
        }
        return $this->_redirect('adminhtml/*/');
    }
}