Default interface methods in C Sharp (C#) - Mini Project: Build & Apply

Using Default Interface Methods in C#

📖 Scenario: Imagine you are building a simple system for different types of devices that can perform actions. You want to define a common interface for devices with a default way to describe themselves.

🎯 Goal: Create an interface with a default method, implement it in a class, and see how the default method works without needing to be overridden.

📋 What You'll Learn

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

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

Use the default Describe() method from the interface without overriding it in the class.

Create an instance of Printer and call both Start() and Describe() methods, then print their outputs.

💡 Why This Matters

🌍 Real World

Default interface methods help add new features to interfaces in large software projects without forcing all existing classes to change.

💼 Career

Understanding default interface methods is important for maintaining and evolving C# codebases in professional software development.

1

Create the IDevice interface with Start() method

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

C Sharp (C#)

// Your code here

Need a hint?

Use the interface keyword and declare void Start(); inside it.

2

Add a default method Describe() to IDevice

Add a default method called Describe() to the IDevice interface that returns the string "This is a device.".

C Sharp (C#)

public interface IDevice
{
    void Start();
    // Your code here
}

Need a hint?

Use a method with a body inside the interface to provide a default implementation.

3

Create Printer class implementing IDevice with Start()

Create a class called Printer that implements IDevice and provide an implementation for the Start() method that returns no value but prints "Printer started." to the console.

C Sharp (C#)

public interface IDevice
{
    void Start();
    
    string Describe()
    {
        return "This is a device.";
    }
}

// Your code here

Need a hint?

Use public class Printer : IDevice and implement the Start() method with a console print.

4

Create Printer instance and call Start() and Describe()

Create an instance of Printer called printer. Call printer.Start() and then print the result of printer.Describe() to the console.

C Sharp (C#)

public interface IDevice
{
    void Start();
    
    string Describe()
    {
        return "This is a device.";
    }
}

public class Printer : IDevice
{
    public void Start()
    {
        System.Console.WriteLine("Printer started.");
    }
}

// Your code here

Need a hint?

Create the Printer object, call Start(), then print Describe() result.