C# Inheritance

Inheritance in C# is an object-oriented programming (OOP) feature that allows one class to derive properties and behaviors from another class. It promotes code reusability, extensibility and establishes a natural hierarchical relationship between classes.

Example: Basic Inheritance

using System;

class Animal {
    public void Eat() {
        Console.WriteLine("This animal eats food.");
    }
}

class Dog : Animal {
    public void Bark() {
        Console.WriteLine("The dog barks.");
    }
}

class Program {
    static void Main() {
        Dog d = new Dog();
        d.Eat();   // Inherited method
        d.Bark();  // Derived class method
    }
}

This animal eats food.
The dog barks.

Syntax

class BaseClass {
// Members of base class
}

class DerivedClass : BaseClass {
// Members of derived class
}

• Inheritance is achieved using the : (colon) symbol.
• Derived Class: The class that inherits the other class is known as a subclass ( or a derived class, extended class or child class).
• Parent Class: The class whose features are inherited is known as a superclass (or a base class or a parent class).
• C# supports single inheritance (a class can directly inherit from only one class).
• A derived class can itself serve as a base for another class.
• All classes in C# implicitly inherit from the System.Object class.

Types of Inheritance

C# directly supports the following inheritance forms:

1. Single Inheritance: One class derives from one base class.
2. Multilevel Inheritance: A class derives from another derived class.
3. Hierarchical Inheritance: Multiple classes derive from a single base class.
4. Multiple Inheritance (Through Interfaces): A class can implement multiple interfaces, achieving multiple inheritance indirectly, since C# does not allow multiple base classes.

1. Single Inheritance

In single inheritance, subclasses inherit the features of one superclass.

In the above image, the class A serves as a base class for the derived class B.

2. Multilevel Inheritance

In Multilevel Inheritance, a derived class will inherit a base class and as well as the derived class also act as the base class for another class.

In the above image, class A serves as a base class for the derived class B, which serves as a base class for the derived class C.

3. Hierarchical Inheritance

In Hierarchical Inheritance, one class serves as a superclass (base class) for more than one subclass.

In the above image, X and Y are sub-class (child class) that inherits property from class B and M and N are sub-class (child class) that inherits property from class C. B is the parent class of X and Y and C is the parent class of M and N.

4. Multiple Inheritance

In Multiple inheritance, one class can have more than one superclass and inherit features from all parent classes.

Please note that C# does not support multiple inheritance with classes. In C#, we can achieve multiple inheritance only through Interfaces.

In the image above, Class C is derived from interfaces A and B.

Advantages of Inheritance

• Code Reusability: Inheritance allows us to reuse existing code by inheriting properties and methods from an existing class.
• Code Maintenance: Inheritance makes code maintenance easier by allowing us to modify the base class and have the changes automatically reflected in the derived classes.
• Code Organization: Inheritance improves code organization by grouping related classes together in a hierarchical structure.

Disadvantages of Inheritance

• Tight Coupling: Inheritance creates a tight coupling between the base class and the derived class, which can make the code more difficult to maintain.
• Complexity: Inheritance can increase the complexity of the code by introducing additional levels of abstraction.
• Fragility: Inheritance can make the code more fragile by creating dependencies between the base class and the derived class.