December 2007
Intermediate to advanced
608 pages
13h 22m
English
Content preview from Programming C# 3.0, 5th EditionBecome an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
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Chapter 5. Inheritance and Polymorphism
The preceding chapter demonstrated how to create new types by declaring classes. This chapter explores the relationship between objects in the real world and how to model these relationships in your code. This chapter focuses on specialization, which is implemented in C# through inheritance. This chapter also explains how instances of more specialized types can be treated as though they were instances of more general types, a process known as polymorphism. This chapter ends with a consideration of sealed classes, which can't be specialized; abstract classes, which exist only to be specialized; and the root of all classes, the Object type.
Tip
VB 6 programmers take note: like VB.NET, C# provides full object-oriented technology, including inheritance, polymorphism, and encapsulation. These are relatively new topics for VB 6 programmers. You should study them carefully; they affect your class and application design.
Specialization and Generalization
Classes and their instances (objects) don't exist in a vacuum, but rather in a network of interdependencies and relationships, just as we, as social animals, live in a world of relationships and categories.
The is-a relationship is one of specialization. When we say that a dog is-a mammal, we mean that the dog is a specialized kind of mammal. It has all the characteristics of any mammal (it bears live young, nurses with milk, has hair), but it specializes these characteristics to the familiar characteristics ...
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I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.