Topic 10. Abstract classes and interfaces

Goal: become familiar with abstract classes and interfaces in C#; learn to declare abstract members, implement the template method, and declare and implement interfaces, including explicitly; master the standard .NET interfaces IComparable<T>, IComparer<T>, and IDisposable with the using statement.

Lecture contents

1. Abstraction and abstract classes — Abstraction · Abstract classes
2. Interfaces — Interfaces
3. Standard interfaces and choosing an approach — Standard .NET interfaces · Abstract class or interface
4. Examples and common mistakes — Example programs · Common mistakes

Practice and review

• Practice — 3 worked examples with complete code and output
• Tasks — 30 variants, each with tasks at three difficulty levels
• Summary — conclusions, self-check questions, and useful links