Inheritance, Interfaces, Polymorphism, and Records

Inheritance and Base Classes

public class Animal
{
    public virtual void Speak() => Console.WriteLine("Animal sound");
}

public class Dog : Animal
{
    public override void Speak() => Console.WriteLine("Woof");
}

Inheritance models shared behavior, but should be used carefully. Composition is often better when direct subtype relationships are weak or unstable.

Interfaces

public interface IPaymentProcessor
{
    void Pay(decimal amount);
}

Interfaces are central in C# architecture because they allow clear contracts, dependency injection, mocking, and flexible implementations.

Polymorphism

Polymorphism allows code to work through abstractions. A service that depends on an interface can use different implementations without rewriting the calling logic.

Records

public record UserDto(int Id, string Name);

Records are useful for immutable data models, DTOs, and message-like structures. They reduce boilerplate and express intent clearly in modern C# code.

Choosing Between Class, Interface, and Record

Real-World Usage Snapshot

These constructs appear constantly in ASP.NET services, enterprise applications, clean architecture implementations, SDKs, and event-driven systems. Modern C# development depends heavily on interface-driven design and record-based data modeling.