Inheritance, Polymorphism, virtual & override Masterclass

⚡ C# 12 & .NET 8 🟢 Chapter 17 of 35 📂 Phase 6: Methods & OOP 📅 2026 Edition

📌 Covered in this chapter: Base & Derived Classes · base Keyword · virtual & override · Runtime Polymorphism · Abstract Classes · Upcasting & Downcasting · OOP Pillars

Welcome to Phase 6 (Chapter 17): C# Inheritance, Polymorphism, virtual & override Masterclass! Inheritance allows a derived class to inherit fields and methods from a base class. Polymorphism allows objects of different derived types to be treated through a single base class reference. C# OOP is founded on four major principles: Abstraction, Encapsulation, Inheritance, and Polymorphism.

1Inheritance & Virtual Method Overriding

C# — Virtual Method Overriding ▶ Run in Compiler

class Animal
{
    public string Name { get; set; }

    public Animal(string name)
    {
        Name = name;
    }

    public virtual void MakeSound()
    {
        Console.WriteLine("Animal makes a sound");
    }
}

class Dog : Animal
{
    public Dog(string name) : base(name) { }

    public override void MakeSound()
    {
        Console.WriteLine($"{Name} barks: Woof! Woof!");
    }
}

Animal animal = new Dog("Buddy");
animal.MakeSound(); // Output: Buddy barks: Woof! Woof!

2Abstract Classes & Methods

C# — Abstract Class Example ▶ Run in Compiler

abstract class Shape
{
    public abstract double CalculateArea(); // Abstract method (no body!)
}

class Circle : Shape
{
    public double Radius { get; set; }
    public Circle(double r) => Radius = r;

    public override double CalculateArea() => Math.PI * Radius * Radius;
}

Shape s = new Circle(5.0);
Console.WriteLine($"Circle Area: {s.CalculateArea():F2}");

3Technical FAQs

Q1: What are the four major OOP principles in C#?

Abstraction, Encapsulation, Inheritance, and Polymorphism.

Q2: Can I instantiate an abstract class?

No! Abstract classes cannot be instantiated with new. They serve as base templates for derived classes.