5.6 Inheritance

Let’s go through inheritance in C# — a key pillar of object-oriented programming (OOP).

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📌 1. What is Inheritance?

Inheritance allows a class (child/derived class) to reuse fields, properties, and methods from another class (parent/base class).

• Promotes code reuse

• Establishes is-a relationships between classes

• Derived classes can override or extend functionality of base classes

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📌 2. Basic Syntax

class BaseClass
{
    // Base class members
}
 
class DerivedClass : BaseClass
{
    // Derived class members
}

• The : symbol indicates inheritance

• DerivedClass inherits all accessible members of BaseClass

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📌 3. Example: Simple Inheritance

// Base class
public class Animal
{
    public string Name;
 
    public void Eat()
    {
        Console.WriteLine($"{Name} is eating.");
    }
}
 
// Derived class
public class Dog : Animal
{
    public void Bark()
    {
        Console.WriteLine($"{Name} is barking.");
    }
}
 
// Usage
Dog dog = new Dog();
dog.Name = "Buddy";
dog.Eat();   // Inherited from Animal
dog.Bark();  // Defined in Dog

• Dog inherits Name and Eat() from Animal

• Can add new behavior (Bark())

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📌 4. Access Modifiers and Inheritance

• public members → accessible in derived class

• protected members → accessible in derived class, but not outside

• private members → not accessible in derived class

public class Animal
{
    protected string species;  // Accessible in derived class
    private int age;           // Not accessible in derived class
}

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📌 5. Method Overriding with virtual and override

• virtual in base class → allows method to be overridden

• override in derived class → provides new behavior

public class Animal
{
    public virtual void MakeSound()
    {
        Console.WriteLine("Some generic sound");
    }
}
 
public class Dog : Animal
{
    public override void MakeSound()
    {
        Console.WriteLine("Bark!");
    }
}
 
// Usage
Animal a = new Dog();
a.MakeSound(); // Bark!

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📌 6. base Keyword

• Access base class members from derived class

public class Dog : Animal
{
    public void ShowName()
    {
        Console.WriteLine(base.Name); // Access Name from base class
    }
}

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📌 7. Summary Table

Concept	Description
Base class	Class whose members are inherited
Derived class	Class that inherits members from base class
Inheritance	Mechanism to reuse code & extend behavior
virtual	Allows method in base class to be overridden
override	Replaces base class implementation in derived class
base	Access base class members in derived class

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✅ Tip:

• Use inheritance to avoid code duplication

• Combine with polymorphism for flexible designs

• Prefer protected for members you want subclasses to access safely