Basic Inheritance (:) Syntax

Part of the Object Oriented Programming section of Coddy's C# journey — lesson 19 of 70.

Inheritance allows a class to acquire the properties and methods of another class. Instead of rewriting the same code, you create a base class (parent) with shared functionality, then create derived classes (children) that inherit from it.

In C#, you use the colon : symbol to indicate inheritance:

public class Animal
{
    public string Name { get; set; }
    
    public void Eat()
    {
        Console.WriteLine($"{Name} is eating.");
    }
}

public class Dog : Animal
{
    public void Bark()
    {
        Console.WriteLine($"{Name} says Woof!");
    }
}

The Dog class inherits everything from Animal. It has access to the Name property and Eat() method without declaring them again, plus it adds its own Bark() method:

Dog myDog = new Dog();
myDog.Name = "Buddy";
myDog.Eat();   // Output: Buddy is eating.
myDog.Bark();  // Output: Buddy says Woof!

C# supports single inheritance only, meaning a class can inherit from just one base class. However, you can build inheritance chains where a derived class becomes the base for another class. This creates a hierarchy that models real-world relationships while keeping your code organized and reusable.

Challenge

Easy

Let's build a vehicle hierarchy that demonstrates how inheritance allows derived classes to share functionality from a base class while adding their own unique behaviors.

You'll create three files to organize your code:

Vehicle.cs: Define a Vehicle class in the Transport namespace. This will be your base class that all vehicles share. It should have a Brand property (string) and a Year property (int), along with a method StartEngine() that prints "{Brand} engine started."
Car.cs: Define a Car class in the Transport namespace that inherits from Vehicle. The car adds its own property NumberOfDoors (int) and a method Honk() that prints "{Brand} goes Beep Beep!"
Program.cs: In your main file, create a Car instance using input values. Set its properties (including the inherited ones), then demonstrate that the car can use both its own methods and the methods it inherited from Vehicle.

You will receive three inputs:

Brand name
Year
Number of doors

Print the car's information and demonstrate its capabilities in this format:

Car: {Brand} ({Year})
Doors: {NumberOfDoors}
{StartEngine output}
{Honk output}

For example, if the inputs are Toyota, 2022, and 4, the output should be:

Car: Toyota (2022)
Doors: 4
Toyota engine started.
Toyota goes Beep Beep!

Notice how your Car can access the Brand property and StartEngine() method even though they're defined in Vehicle. That's the power of inheritance - the derived class automatically gets everything from its base class!

Cheat sheet

Inheritance allows a class to acquire properties and methods from another class using the colon : symbol:

public class Animal
{
    public string Name { get; set; }
    
    public void Eat()
    {
        Console.WriteLine($"{Name} is eating.");
    }
}

public class Dog : Animal
{
    public void Bark()
    {
        Console.WriteLine($"{Name} says Woof!");
    }
}

The derived class (Dog) inherits all properties and methods from the base class (Animal) and can add its own:

Dog myDog = new Dog();
myDog.Name = "Buddy";
myDog.Eat();   // Inherited method
myDog.Bark();  // Own method

C# supports single inheritance only - a class can inherit from just one base class. However, you can create inheritance chains to build hierarchies.

Try it yourself

using System;
using Transport;

class Program
{
    public static void Main(string[] args)
    {
        // Read input
        string brand = Console.ReadLine();
        int year = Convert.ToInt32(Console.ReadLine());
        int doors = Convert.ToInt32(Console.ReadLine());
        
        // TODO: Create a Car instance
        
        // TODO: Set the car's properties (Brand, Year, NumberOfDoors)
        
        // TODO: Print the car's information in the required format:
        // Car: {Brand} ({Year})
        // Doors: {NumberOfDoors}
        // Then call StartEngine() and Honk()
    }
}