Abstract Class vs Interface Interface Meaning Defines capability and behavior contract Use when: ● Multiple inheritance is required ● System uses plug-in extensibility ● Loose coupling is necessary public interface IPayment { void Pay(decimal amount); }

bstract Class Meaning

Provides base behavior with shared implementation

Represents IS-A inheritance relationship

public abstract class PaymentBase
{
public void Log() => Console.WriteLine("Payment logged");
public abstract void Pay(decimal amount);
}

Summary

Interface = Capability

bstract Class = Shared Base Behavior