Generics

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If you're a C# programmer looking to add some more power to your code, you might want to consider learning how to use generics. This article, the first part of a three-part series, explains what they are and how to use them. It is excerpted from chapter four of the C# 3.0 Cookbook, Third Edition, written by Jay Hilyard and Stephen Teilhet (O'Reilly, 2008; ISBN: 059651610X). Copyright © 2008 O'Reilly Media, Inc. All rights reserved. Used with permission from the publisher. Available from booksellers or direct from O'Reilly Media.

4.0 Introduction

Generics are an extremely useful feature that allows you to write type safe and efficient collection- and pattern-based code. This aspect of generics is described in Recipes 4.1 and 4.2. With generics comes quite a bit of programming power, but with that power comes the responsibility to use it correctly. If you are considering converting your ArrayList, Queue, Stack, andHashtable objects to use their generic counterparts, consider reading Recipes 4.3, 4.4, and 4.9. As you will read, the conversion is not always simple and easy, and there are reasons why you might not want to do this conversion at all.

Some recipes in this chapter, such as Recipe 4.5, deal with other generic classes contained in the .NET Framework. Still, others deal with the operation of any generic type; see Recipes 4.1, 4.7, and 4.11.

4.1   Deciding When and Where to Use Generics

Problem

You want to use generic types in a new project or convert nongeneric types in an existing project to their generic equivalent. However, you do not really know why you would want to do this, and you do not know which nongeneric types should be converted to be generic.

Solution

In deciding when and where to use generic types, you need to consider several things:

1. Will your type contain or be operating on various unspecified data types (e.g., a collection type)? If so, creating a generic type will offer several benefits over creating a nongeneric type. If your type will operate on only a single specific type, then you may not need to create a generic type.
   
2. If your type will be operating on value types, so that boxing and unboxing operations will occur, you should consider using generics to prevent the boxing and unboxing operations.
   
3. The stronger type checking associated with generics will aid in finding errors sooner (i.e., during compile time as opposed to runtime), thus shortening your bug-fixing cycle.
   
4. Is your code suffering from “code bloat,” with you writing multiple classes to handle different data types on which they operate (e.g., a specializedArrayListthat stores onlyStreamReadersand another that stores onlyStreamWriters)? It is easier to write the code once and have it just work for each of the data types it operates on.
   
5. Generics allow for greater clarity of code. By eliminating code bloat and forcing stronger type checking on your types, your code will be easier to read and understand.

Discussion

In most cases, your code will benefit from using a generic type. Generics allow for more efficient code reuse, faster performance, stronger type checking, and easier-to-read code.

See Also

The “Generics Overview” and “Benefits of Generics” topics in the MSDN documentation.

Next: 4.2 Understanding Generic Types >>
 

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