Understanding Inheritance and Polymorphism in C

1. Introduction

This tutorial aims to provide an in-depth understanding of two fundamental object-oriented programming concepts: inheritance and polymorphism, using C# as the language of choice.

By the end of this tutorial, you will be able to:

• Understand the concept of inheritance and how to create subclasses in C#
• Understand the concept of polymorphism and how to override methods
• Utilize inheritance and polymorphism to create more efficient and organized code

Prerequisites: A basic understanding of C# syntax and object-oriented programming concepts such as classes and objects.

2. Step-by-Step Guide

Inheritance

Inheritance allows us to define a class in terms of another class, which makes creating and maintaining an application easier. This also provides an opportunity to reuse the code functionality and fast implementation time.

// Base class
public class Animal {
    public virtual void animalSound() {
        Console.WriteLine("The animal makes a sound");
    }
}

Here, Animal is a base class, and the function animalSound() is marked as virtual, which means it can be overridden in the subclass.

Polymorphism

Polymorphism means "many forms", and it occurs when we have many classes that are related to each other by inheritance.

// Derived classes
public class Pig : Animal {
    public override void animalSound() {
        Console.WriteLine("The pig says: wee wee");
    }
}

public class Dog : Animal {
    public override void animalSound() {
        Console.WriteLine("The dog says: bow wow");
    }
}

Here, Pig and Dog are derived classes that inherit from the Animal base class. Both classes override the animalSound() method.

3. Code Examples

Code Example 1

// Driver code
public class Program {
    public static void Main(string[] args) {
        Animal myAnimal = new Animal();  // Create a Animal object
        Animal myPig = new Pig();  // Create a Pig object
        Animal myDog = new Dog();  // Create a Dog object

        myAnimal.animalSound();  // Animal: The animal makes a sound
        myPig.animalSound();  // Pig: The pig says: wee wee
        myDog.animalSound();  // Dog: The dog says: bow wow
    }
}

This is the driver code, where we create objects of the Animal, Pig, and Dog classes, and call their animalSound() methods. The output will be as commented in the code.

4. Summary

In this tutorial, we've covered the basics of inheritance and polymorphism. We've learned how to create subclasses, how to override methods, and how to make efficient use of these concepts to make our code more organized and reusable.

Next, you can explore other object-oriented concepts like abstraction and encapsulation.

5. Practice Exercises

Exercise 1: Create a base class Car with a method carSound() that outputs "The car makes a sound". Create two subclasses BMW and Mercedes that override the carSound() method to output "BMW says: brum brum" and "Mercedes says: vroom vroom", respectively.

Exercise 2: Modify the Car class to include a model property. Add a constructor method to each subclass that accepts a model parameter and sets the model property. Override the carSound() method in each subclass to include the model in the output, for example, "The BMW X5 says: brum brum".

Exercise 3: Create a list of Car objects that includes instances of both the BMW and Mercedes subclasses. Loop over the list and call the carSound() method for each object.

Note: Practice is essential in learning programming. Try to modify the code or experiment with it to see different outcomes.