How can load Model function in block when overide or extend a core magento block

Question

Please Explain me in Magento 2.0 (Only Override Case)

Answer 1

Following way you can get object manager instance

$objectManager = \Magento\Framework\App\ObjectManager::getInstance();

Now you can get/create any model or model collection. Here is an example of order collection.

$orderCollection = $objectManager->get('Magento\Sales\Model\Order')->getCollection()

Answer 2

In Magento 2 constructor is not part of public API and you can change it (add more dependencies). And you should do not call ObjectManager direct.

in your case, add constructor with order factory

public function __construct(
    \Magento\Framework\View\Element\Template\Context $context,
    \Magento\Directory\Helper\Data $directoryHelper,
    \Magento\Framework\Json\EncoderInterface $jsonEncoder,
    \Magento\Framework\App\Cache\Type\Config $configCacheType,
    \Magento\Directory\Model\ResourceModel\Region\CollectionFactory $regionCollectionFactory,
    \Magento\Directory\Model\ResourceModel\Country\CollectionFactory $countryCollectionFactory,
    \Magento\Framework\Module\Manager $moduleManager,
    \Magento\Customer\Model\Session $customerSession,
    \Magento\Customer\Model\Url $customerUrl,
    \Magento\Sales\Model\ResourceModel\Order\CollectionFactory $collectionFactory,
    array $data = []
) {
   parent::__construct(...);
   $this->collectionFactory = $collectionFactory;

and in method hello use it

public function hello()
{
    return $this->collectionFactory->create()->load();
}