C# object-oriented programming

Use encapsulation to protect invariants and interfaces to express contracts. Learn how access modifiers and static members affect dependencies before building complicated hierarchies.

Lessons and practical examples

• Abstract classes and interfaces: Abstraction, interface contracts, multiple interfaces and implementation choices.

• Access modifiers explained: public, private, protected, internal, protected internal, private protected and file.

• Classes, objects and constructors: Objects, fields, class members, constructors, files and partial classes.

• Inheritance and polymorphism: Base classes, derived classes, virtual, override, base and polymorphic calls.

• Properties and encapsulation: get, set, init, private set, auto-properties and validation.

• Static, const and readonly: What public static int means, shared fields, compile-time constants and read-only state.

How to study this section

Start with one concept, work through a small example, and verify your prediction. Follow linked topics when a prerequisite or related idea needs more explanation.