[TYPO3-mvc] Typo3 extbase validating custom or manual objects

[Ganapati Bhat]

I have created extbase extension, there for some reason I need to create
object manually in create action.

My create action looks like this,

/**
* action create
*
* @return void
*/
public function createAction() {
$newObj = new \TYPO3\Myext\Domain\Model\Modelname();
$newObj->setMyval('value');
$this->myrepository->add($newObj);
}

Here the problem is its not validating for require field, captcha etc.
So how to make the validation of manually created object ?
It should throw error to form like out-of-the-box features, before add()
function, if there is a validation error.

Thank you.

Regards,
Ganybhat