Mediator Interface (IChatMediator):?

Short answer: The IChatMediator interface defines two key operations: ■ SendMessage(string message, User user): Sends a message from a user to all other registered users. ■ RegisterUser(User user): Registers users with the mediator so they can send and receive messages. public interface IChatMediator

Example code

{ void SendMessage(string message, User user); void RegisterUser(User user); }

Real-world example (ShopNest)

Use a GoF pattern in ShopNest only when it removes duplication or makes a change safer—explain the problem it solves in the interview.

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.