C# Inheritance

Summary: in this tutorial, you’ll learn about C# inheritance that allows a class to reuse the properties and methods of another class.

Introduction to the C# inheritance

Inheritance is one of the core concepts in object-oriented programming. Inheritance allows a class to inherit from another class.

Inheriting from a class allows you to reuse the functionality of the class instead of building it from scratch.

C# allows a class to inherit only from a single class. This is called single inheritance. C# doesn’t support multiple inheritances where a class can inherit from two or more classes.

Suppose you have a Person class with properties FirstName, LastName, Age, and FullName and a method Introduce():

// Person.cs
class Person
{
    public string FirstName { get; set; }

    public string LastName { get; set; }

    public byte Age { get; set; }

    public string FullName => $"{FirstName} {LastName}";

    public string Introduce() => $"Hi, I'm {FullName}.";
    
}Code language: C# (cs)

And you want to define an Employee class that has all the properties as the Person class and two more properties JobTitle and Salary.

Instead of copying code from the Employee class to the Employee class, you can use inheritance. The following defines the Employee class that inherits from the Person class:

// Employee.cs

class Employee: Person
{
    
}Code language: C# (cs)

In this example:

• The Person class is called the parent class, a base class, or a super class
• The Employee class is called a child class, derived class, or subclass.

We also say that the Employee class extends the Person class.

Since the Employee class inherits the properties and methods of the Person class, its objects behave like objects of the Person class. For example:

// Program.cs

var employee = new Employee
{
    FirstName = "John",
    LastName = "Doe",
    Age = 25
};

Console.WriteLine(employee.Introduce());Code language: C# (cs)

Output:

Hi, I'm John Doe.Code language: C# (cs)

As you can see, the Employee behaves like the Person class without duplicating the code. We say that an employee is a person. And the inheritance models an is-a relationship.

Extending a parent class

The following adds the JobTitle and Salary properties to the Employee class:

// Employee.cs
class Employee : Person
{
    public string JobTitle { get; set; }
    public decimal Salary { get; set; }
}Code language: C# (cs)

Now, the Employee class has its own properties and the inherited properties from the Person class. The following creates a new instance of the Employee class with all the properties:

// Program.cs

var employee = new Employee
{
    FirstName = "John",
    LastName = "Doe",
    Age = 25,
    JobTitle = "C# Developer",
    Salary = 120000
};

Console.WriteLine(employee.Introduce());Code language: C# (cs)

Output:

Hi, I'm John Doe.Code language: C# (cs)

Summary

• Inheritance allows a class (subclass) to inherit from another class (base class) to extend or customize the base class.
• C# allows a class to inherit from a single class. This is called the single inheritance.