11. OOP Principles#
Classes alone do not make a program object-oriented. This chapter names and illustrates the core object-oriented principles: encapsulation, inheritance, polymorphism, and abstraction, with concrete C# examples.
Encapsulation: Objects protect their internal state and expose a controlled public surface.
Inheritance: A derived class can reuse and specialize behavior from a base class.
Polymorphism: Code can work with a general type while runtime objects provide specific behavior.
Abstraction: Interfaces and abstract classes describe capabilities without committing to one implementation.
Composition: Modern C# often favors combining small objects over building deep inheritance trees.
The goal is conceptual clarity and practical design judgment, especially knowing when interfaces and composition are cleaner than deep hierarchies.
Video
C# for Beginners – Lesson 15: Inheritance, Polymorphism & Abstraction by Mike’s Code.
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Learning Objectives
By the end of this chapter, you will be able to:
Explain the four major object-oriented principles with concrete examples
Relate encapsulation to the class design practiced in the Classes chapter
Create a small inheritance hierarchy with base and derived classes
Use overriding or interfaces to support polymorphic behavior
Explain why composition and interfaces are often preferred over deep inheritance