C# Inheritance

C# Inheritance

Inheritance is an Object Oriented Programming concept in which a class can inherit the properties and methods of another class.

Usually, the inheriting class is called derived class. And the class which is inherited is called base class.

The derived class can use, extend or override the properties and methods of its base class.

Inheritance can be used when your use cases have categorical and sub-categorical objects.

Example 1 – C# Inheritance

This example demonstrates the usage of inheritance concept in C# programming.

Consider that our application deals with production line of cars. We will define a base class of Car and a derived class of SportsCar. A sports car can be considered as a sub-category of car in general.

We will have some properties and methods in Car class. And SportsCar class will override some of the methods, and have new methods of its own.

Program.cs

using System;

namespace CSharpExamples {
    class Car {
        public int chasis_number;
        public string name;
        public void addWheels(){
            Console.WriteLine("4 wheels added.");
        }
        public void addSeats(){
            Console.WriteLine("4 seats added.");
        }
    }

    class SportsCar: Car {
        public string name;

        public SportsCar(int chasis_number, string name){
            this.name = name;
            this.chasis_number = chasis_number;
        }
        public void addSeats(){
            Console.WriteLine("2 seats added.");
        }

        public void printDetails(){
            Console.WriteLine("\nCar Details\n------------");
            Console.WriteLine("Chasis Number : " + this.chasis_number);
            Console.WriteLine("Car Name : " + this.name);
        }
    }

    class Program {
        static void Main(string[] args) {
            SportsCar car1 = new SportsCar(254, "McLaren 570S");
            car1.addSeats();
            car1.addWheels();
            car1.printDetails();
        }
    }
}

Base Class: Car. Car has two properties: chasis_number and name. Car has two methods: addWheels(), addSeats().

Derived Class: SportsCar. SportsCar inherits Car class. But SportsCar overrides the property name and method addSeats(). It has an additional method printDetails(). SportsCar class has constructor.

Output

2 seats added.
4 wheels added.

Car Details
------------
Chasis Number : 254
Car Name : McLaren 570S

Example 2 – About Overridden Properties

If you override a property, you cannot access that property in the method of base class.

Consider the above example. We have printDetails() method in derived class. And in printDetails() class, we are accessing the overridden property name. If we have the same printDetails() function in base class, we cannot access name property.

This is because, we can access properties of base class in derived class, but cannot access properties of derived class in base class. As we have overridden the property name, we cannot access this in our base class.

Program.cs

using System;

namespace CSharpExamples {
    class Car {
        public int chasis_number;
        public string name;
        public void addWheels(){
            Console.WriteLine("4 wheels added.");
        }
        public void addSeats(){
            Console.WriteLine("4 seats added.");
        }
        public void printDetails(){
            Console.WriteLine("\nCar Details\n------------");
            Console.WriteLine("Chasis Number : " + this.chasis_number);
            Console.WriteLine("Car Name : " + this.name);
        }
    }

    class SportsCar: Car {
        public string name;

        public SportsCar(int chasis_number, string name){
            this.name = name;
            this.chasis_number = chasis_number;
        }
        public void addSeats(){
            Console.WriteLine("2 seats added.");
        }
    }

    class Program {
        static void Main(string[] args) {
            SportsCar car1 = new SportsCar(254, "McLaren 570S");
            car1.addSeats();
            car1.addWheels();
            car1.printDetails();
        }
    }
}

Output

2 seats added.
4 wheels added.

Car Details
------------
Chasis Number : 254
Car Name :

You might observe the following warnings before the actual output shown above.

Program.cs(21,23): warning CS0108: 'SportsCar.name' hides inherited member 'Car.name'. Use the new keyword if hiding was intended. [D:\workspace\csharp\HelloWorld\HelloWorld.csproj]
Program.cs(27,21): warning CS0108: 'SportsCar.addSeats()' hides inherited member 'Car.addSeats()'. Use the new keyword if hiding was intended. [D:\workspace\csharp\HelloWorld\HelloWorld.csproj]
Program.cs(6,23): warning CS0649: Field 'Car.name' is never assigned to, and will always have its default value null [D:\workspace\csharp\HelloWorld\HelloWorld.csproj]

Conclusion

In this C# Tutorial, we have learned what Inheritance is in Object Oriented Programming, how to implement Inheritance in C# programming, and some of the implementations with example programs.