Interface vs abstract class decision in C Sharp (C#) - Hands-On Comparison

Interface vs Abstract Class Decision in C#

📖 Scenario: Imagine you are building a simple program for a zoo management system. You need to model different animals and their behaviors. Some animals can fly, some can swim, and some can do both. You want to decide when to use an interface and when to use an abstract class to organize these behaviors.

🎯 Goal: You will create an abstract class and an interface in C# to represent animal behaviors, then implement them in specific animal classes. This will help you understand when to use interfaces and when to use abstract classes.

📋 What You'll Learn

Create an abstract class called Animal with a method MakeSound().

Create an interface called IFlyable with a method Fly().

Create a class Bird that inherits from Animal and implements IFlyable.

Create a class Fish that inherits from Animal.

Implement the methods to print simple messages describing the actions.

Create instances of Bird and Fish and call their methods.

💡 Why This Matters

🌍 Real World

In real software, you often need to organize code so that different objects share some behaviors but also have unique abilities. Abstract classes and interfaces help you do this clearly and safely.

💼 Career

Understanding when to use interfaces versus abstract classes is a key skill for software developers, especially in object-oriented programming languages like C#. It helps in designing clean, maintainable, and flexible code.

1

Create the abstract class Animal

Create an abstract class called Animal with an abstract method MakeSound() that returns void.

C Sharp (C#)

abstract class Animal
{
    // Your code here
}

Need a hint?

Use the abstract keyword before the class and method. The method should have no body.

2

Create the interface IFlyable

Create an interface called IFlyable with a method Fly() that returns void.

C Sharp (C#)

abstract class Animal
{
    public abstract void MakeSound();
}

interface IFlyable
{
    // Your code here
}

Need a hint?

Interfaces do not have access modifiers on methods. Just declare the method signature.

3

Create classes Bird and Fish

Create a class called Bird that inherits from Animal and implements IFlyable. Implement the methods MakeSound() to print "Bird chirps" and Fly() to print "Bird is flying". Also create a class called Fish that inherits from Animal and implements MakeSound() to print "Fish blubs".

C Sharp (C#)

abstract class Animal
{
    public abstract void MakeSound();
}

interface IFlyable
{
    void Fly();
}

class Bird : Animal, IFlyable
{
    // Your code here
}

class Fish : Animal
{
    // Your code here
}

Need a hint?

Use override keyword to implement abstract methods. Implement interface methods normally.

4

Create instances and call methods

Create an instance of Bird called bird and an instance of Fish called fish. Call MakeSound() on both. Call Fly() on bird.

C Sharp (C#)

abstract class Animal
{
    public abstract void MakeSound();
}

interface IFlyable
{
    void Fly();
}

class Bird : Animal, IFlyable
{
    public override void MakeSound()
    {
        System.Console.WriteLine("Bird chirps");
    }

    public void Fly()
    {
        System.Console.WriteLine("Bird is flying");
    }
}

class Fish : Animal
{
    public override void MakeSound()
    {
        System.Console.WriteLine("Fish blubs");
    }
}

// Your code here

Need a hint?

Create objects using new keyword and call methods with dot notation.