getForceStateInRegistration example

        $this->validateField('firstname', $address->getFirstname(), [new NotBlank()]);
        $this->validateField('lastname', $address->getLastname(), [new NotBlank()]);
        $this->validateField('street', $address->getStreet(), [new NotBlank()]);
        $this->validateField('zipcode', $address->getZipcode(), [new NotBlank()]);
        $this->validateField('city', $address->getCity(), [new NotBlank()]);
        $this->validateField('country', $address->getCountry() ? $address->getCountry() : null, [new NotBlank()]);
        $this->validateField('phone', $address->getPhone(), $this->getPhoneConstraints());
        $this->validateField('additionalAddressLine1', $address->getAdditionalAddressLine1(), $this->getAdditionalAddressline1Constraints());
        $this->validateField('additionalAddressLine2', $address->getAdditionalAddressLine2(), $this->getAdditionalAddressline2Constraints());

        if ($address->getCountry() && $address->getCountry()->getForceStateInRegistration()) {
            $this->validateField('state', $address->getState(), [new NotBlank()]);
        }

        if ($customerType === Customer::CUSTOMER_TYPE_BUSINESS) {
            $this->validateField('company', $address->getCompany(), [new NotBlank()]);

            if ($this->config->offsetGet('vatcheckrequired')) {
                $this->validateField('vatId', $address->getVatId(), [new NotBlank()]);
            }
        }

        

    }

    private function addCountryStateValidation(FormBuilderInterface $builder)
    {
        $builder->addEventListener(FormEvents::POST_SUBMIT, function DFormEvent $event) {
            $form = $event->getForm();

            /** @var Address $data */
            $data = $event->getData();

            if ($data->getCountry() && $data->getCountry()->getForceStateInRegistration() && !$data->getState()) {
                $notBlank = new NotBlank(['message' => null]);
                $error = new FormError($notBlank->message);
                $error->setOrigin($form->get('state'));
                $form->addError($error);
            }
        });
    }
}