Decorator (CoffeeDecorator):?

Short answer: The CoffeeDecorator class is an abstract class that implements the ICoffee interface and holds a reference to an ICoffee object. This class allows us to add additional behavior to the coffee object, but we don't modify the base class (SimpleCoffee). public abstract class CoffeeDecorator : ICoffee

Example code

{ protected ICoffee _coffee; protected CoffeeDecorator(ICoffee coffee) => _coffee = coffee;
public virtual double Cost() => _coffee.Cost();
public virtual string Description() => _coffee.Description();
}

Real-world example (ShopNest)

Logging and caching decorators wrap IProductRepository so core SQL code stays clean.

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.