How would you use polymorphism to handle different file formats?

Short answer: Define abstract class FileHandler with method Read(). Derived classes CsvHandler, XmlHandler implement Read(). Use base class reference to process files uniformly.

Real-world example (ShopNest)

Checkout calls IPaymentGateway.Charge(). Razorpay and Stripe adapters implement the same interface, so ShopNest can switch gateways without rewriting the order service.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.