Unhold.php

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

class Unhold extends \Magento\Sales\Controller\Adminhtml\Order
{
    /**
     * Authorization level of a basic admin session
     *
     * @see _isAllowed()
     */
    const ADMIN_RESOURCE = 'Magento_Sales::unhold';

    /**
     * Unhold order
     *
     * @return \Magento\Backend\Model\View\Result\Redirect
     */
    public function execute()
    {
        $resultRedirect = $this->resultRedirectFactory->create();
        if (!$this->isValidPostRequest()) {
            $this->messageManager->addErrorMessage(__('Can\'t unhold order.'));
            return $resultRedirect->setPath('sales/*/');
        }
        $order = $this->_initOrder();
        if ($order) {
            try {
                if (!$order->canUnhold()) {
                    throw new \Magento\Framework\Exception\LocalizedException(__('Can\'t unhold order.'));
                }
                $this->orderManagement->unHold($order->getEntityId());
                $this->messageManager->addSuccessMessage(__('You released the order from holding status.'));
            } catch (\Magento\Framework\Exception\LocalizedException $e) {
                $this->messageManager->addErrorMessage($e->getMessage());
            } catch (\Exception $e) {
                $this->messageManager->addErrorMessage(__('The order was not on hold.'));
            }
            $resultRedirect->setPath('sales/order/view', ['order_id' => $order->getId()]);
            return $resultRedirect;
        }
        $resultRedirect->setPath('sales/*/');
        return $resultRedirect;
    }
}