Why interfaces are needed in C Sharp (C#) - See It in Action

Why interfaces are needed

📖 Scenario: Imagine you are building a simple app that manages different types of devices like printers and scanners. Each device can perform an action called Start, but the way they start is different. You want a way to make sure every device has a Start action, so your app can use any device without worrying about its details.

🎯 Goal: You will create an interface called IDevice that requires a Start method. Then, you will create two classes, Printer and Scanner, that implement this interface. Finally, you will write code to start each device using the interface, showing why interfaces help organize code and make it flexible.

📋 What You'll Learn

Create an interface called IDevice with a method Start().

Create a class Printer that implements IDevice and its Start() method.

Create a class Scanner that implements IDevice and its Start() method.

Create a list of IDevice containing one Printer and one Scanner.

Use a foreach loop to call Start() on each device and print the result.

💡 Why This Matters

🌍 Real World

Interfaces are used in software to make sure different parts of a program can work together smoothly, like different devices in a system.

💼 Career

Understanding interfaces is important for writing clean, flexible code in many programming jobs, especially in object-oriented programming.

1

Create the IDevice interface

Create an interface called IDevice with a method Start() that returns a string.

C Sharp (C#)

// Your code here

Need a hint?

An interface is like a contract. It tells classes what methods they must have.

2

Create Printer and Scanner classes implementing IDevice

Create a class called Printer that implements IDevice and its Start() method returning the string "Printer is starting". Also create a class called Scanner that implements IDevice and its Start() method returning the string "Scanner is starting".

C Sharp (C#)

public interface IDevice
{
    string Start();
}

// Your code here

Need a hint?

Use : IDevice after the class name to say it implements the interface.

3

Create a list of IDevice with Printer and Scanner

Create a list called devices of type List<IDevice> and add one Printer and one Scanner object to it.

C Sharp (C#)

public interface IDevice
{
    string Start();
}

public class Printer : IDevice
{
    public string Start()
    {
        return "Printer is starting";
    }
}

public class Scanner : IDevice
{
    public string Start()
    {
        return "Scanner is starting";
    }
}

// Your code here

Need a hint?

Use new List<IDevice> { ... } to create the list and add objects inside curly braces.

4

Use a foreach loop to start each device and print the result

Use a foreach loop with variable device to go through devices and print the result of calling device.Start().

C Sharp (C#)

using System.Collections.Generic;

public interface IDevice
{
    string Start();
}

public class Printer : IDevice
{
    public string Start()
    {
        return "Printer is starting";
    }
}

public class Scanner : IDevice
{
    public string Start()
    {
        return "Scanner is starting";
    }
}

List devices = new List { new Printer(), new Scanner() };

// Your code here

Need a hint?

Use Console.WriteLine(device.Start()); inside the loop to print each message.