How to send array of object using postman as a formdata

I am trying to send an array of the object as a form-data using postman. But it's not working. I follow this link in StackOverflow...But it's worked for mt.

When I send my category like this it's sent like this:- Category returns null property.

This should be like this. I got this screenshot when I was passing data application/JSON.

But now I need to send an image with my req, I need to send my req as a form/data. But My Category object array is not passing the way I want, Or the way my system wants. I really need your help. Thank you.