#229 – The Core Principles of Object-Oriented Programming

As an object-oriented language, C# supports the three core principles of object-oriented programming:

• Encapsulation – Hide implementation details in a class from users of the class, exposing only a public interface
• Inheritance – Derive a subclass from a parent class, inheriting data and behavior from the parent, in an “is-a” relationship.  Inheritance defines a hierarchy of classes.  All classes ultimately inherit from System.Object.
• Polymorphism – Any subtype may be used where a parent type (or type higher up in the class hierarchy) is expected.  Conversely, a variable of a particular class will be treated as the appropriate subclass.