Liskov Substitution Principle (LSP)

Objects of a superclass should be replaceable with objects of a subclass without affecting the program.

 

// Violating LSP
public class Bird {
    public virtual void Fly() {
        Console.WriteLine("Bird is flying");
    }
}

public class Ostrich : Bird {
    public override void Fly() {
        throw new NotImplementedException("Ostrich can't fly");
    }
}

// Following LSP
public abstract class Bird {
    public abstract void Move();
}

public class Sparrow : Bird {
    public override void Move() {
        Console.WriteLine("Sparrow is flying");
    }
}

public class Ostrich : Bird {
    public override void Move() {
        Console.WriteLine("Ostrich is running");
    }
}

Liskov Substitution Principle (LSP)

Explanation:

Objects of a superclass should be replaceable with objects of a subclass without affecting the program.

Real-World Example:

If a bird can fly, a sparrow (subclass) should also fly.

C# Implementation: