How do you implement abstraction in C#?

Short answer: Using abstract classes or interfaces. Abstract classes can have abstract and non-abstract methods. Interfaces define method signatures only. abstract class Vehicle { public abstract void Start(); } interface IDriveable { void Drive(); }

Example code

Using abstract classes or interfaces. Abstract classes can have abstract and non-abstract methods. Interfaces define method signatures only. abstract class Vehicle {
public abstract void Start();
}
interface IDriveable
{ void Drive(); }

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.