M2 | Field Validation is not working with dynamic rows in system configuration

Question

I have applied filed validation in system.xml file it is working for other fields but not applying on Dynamic fields.

Here is my Dynamic Field:

 <field id="add_item" translate="label" sortOrder="15" showInDefault="0" showInWebsite="1" showInStore="0">
 <label>Set Dropdown Prices</label>
 <frontend_model>Vendor\Module\Block\Adminhtml\Menu\Field\AdditionalItem</frontend_model>
 <backend_model>Vendor\Module\Block\Adminhtml\Menu\Config\Backend\AdditionalItem</backend_model>
 <validate>validate-digits</validate>
 </field>

Update

Here is my column in Frontend Model:

$this->addColumn(
 'productcost',
 [
 'label' => __('Voucher Cost'),
 'size' => '150px',
 'class' => 'required-entry'
 ]
 );

Answer 1

Move size into style class

 $this->addColumn('productcost', ['label' => __('Voucher Cost'),'class' => 'required-entry validate-number','style' => 'width:50px']);

• Ajwad Syed: required-entry class is already in my frontend model but it has no effect, please see the update in question
• Arunprabakaran M: Kindly share error log
• Ajwad Syed: Yes moving size in style worked for me.. Can u tell how to limit the number of dynamic rows like we should extend it up to 20 rows..
• Arunprabakaran M: Good question Ajwad Taqvi. Kindly post as another question.
• Ajwad Syed: Posted: magento.stackexchange.com/questions/272414/…