Framework Design Guidelines: Conventions, Idioms, and Patterns for Reusable .NET Libraries

Framework Design Guidelines: Conventions, Idioms, and Patterns for Reusable .NET Libraries

by Krzysztof Cwalina, Brad Abrams
     
 

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This is the eBook version of the print title,  Framework Design Guidelines, Second Edition . Access to all the samples, applications, and content on the DVD is available.

 

Framework Design Guidelines, Second Edition, teaches developers the best practices for designing reusable libraries for the

Overview

This is the eBook version of the print title,  Framework Design Guidelines, Second Edition . Access to all the samples, applications, and content on the DVD is available.

 

Framework Design Guidelines, Second Edition, teaches developers the best practices for designing reusable libraries for the Microsoft .NET Framework. Expanded and updated for .NET 3.5, this new edition focuses on the design issues that directly affect the programmability of a class library, specifically its publicly accessible APIs.

 

This book can improve the work of any .NET developer producing code that other developers will use. It includes copious annotations to the guidelines by thirty-five prominent architects and practitioners of the .NET Framework, providing a lively discussion of the reasons for the guidelines as well as examples of when to break those guidelines.

 

Microsoft architects Krzysztof Cwalina and Brad Abrams teach framework design from the top down. From their significant combined experience and deep insight, you will learn

• The general philosophy and fundamental principles of framework design • Naming guidelines for the various parts of a framework • Guidelines for the design and extending of types and members of types • Issues affecting–and guidelines for ensuring–extensibility • How (and how not) to design exceptions • Guidelines for–and examples of–common framework design patterns

Guidelines in this book are presented in four major forms: Do, Consider, Avoid, and Do not. These directives help focus attention on practices that should always be used, those that should generally be used, those that should rarely be used, and those that should never be used. Every guideline includes a discussion of its applicability, and most include a code example to help illuminate the dialogue.

 

Framework Design Guidelines, Second Edition, is the only definitive source of best practices for managed code API development, direct from the architects themselves.

 

A companion DVD includes the Designing .NET Class Libraries video series, instructional presentations by the authors on design guidelines for developing classes and components that extend the .NET Framework. A sample API specification and other useful resources and tools are also included.

 

 

 

Product Details

ISBN-13:
9780321605009
Publisher:
Pearson Education
Publication date:
10/22/2008
Series:
Microsoft Windows Development Series
Sold by:
Barnes & Noble
Format:
NOOK Book
Pages:
480
File size:
1 MB

Read an Excerpt

This book, Framework Design Guidelines, presents best practices for designing frameworks, which are reusable object-oriented libraries. The guidelines are applicable to frameworks ranging in size and in their scale of reuse:

  • Large system frameworks, such as the .NET Framework, usually consisting of thousands of types and used by millions of developers.
  • Medium-size reusable layers of large distributed applications
  • or extensions to system frameworks, such as the Web Services
  • Enhancements.
  • Small components shared among several applications; for example, a grid control library.

It is worth noting that this book focuses on design issues that directly affect the programmability of a framework (publicly accessible APIs). As a result, we generally do not cover much in terms of implementation details. Just like a user interface design book doesn't cover the details of how to implement hit testing, this book does not describe how to implement a binary sort, for example. This scope allows us to provide a definitive guide for framework designers instead of being yet another book about programming.

These guidelines were created in the early days of .NET Framework development. They started as a small set of naming and design conventions but have been enhanced, scrutinized, and refined to a point where they are generally considered the canonical way to design frameworks at Microsoft. They carry the experience and cumulative wisdom of thousands of developer hours over three versions of the .NET Framework. We tried to avoid basing the text purely on some idealistic design philosophies, and we think its day-to-day use by development teams at Microsoft has made it an intensely pragmatic book.

The book contains many annotations that explain trade-offs, explain history, amplify, or provide critiquing views on the guidelines. These annotations are written by experienced framework designers, industry experts, and users. They are the stories from the trenches that add color and setting for many of the guidelines presented.

To make them more easily distinguished in text, namespace names, classes, interfaces, methods, properties, and types are set in monospace font. The book assumes basic familiarity with .NET Framework programming. A few guidelines assume familiarity with features introduced in version 2.0 of the Framework. If you are looking for a good introduction to Framework programming, there are some excellent suggestions in the Suggested Reading List at the end of the book.

Guideline Presentation

The guidelines are organized as simple recommendations using Do, Consider, Avoid, and Do not. Each guideline describes either a good or bad practice and all have a consistent presentation. Good practices have a check mark in front of them, and bad practices have an X in front of them. The wording of each guideline also indicates how strong the recommendation is. For example, a Do guideline is one that should always1 be followed (all examples are from this book):

DO name custom attribute classes with the suffix "Attribute."

public class ObsoleteAttribute : Attribute { ... }

On the other hand, Consider guidelines should generally be followed, but if you fully understand the reasoning behind a guideline and have a good reason to not follow it anyway, you should not feel bad about breaking the rules:

CONSIDER defining a struct instead of a class if instances of the type are small and commonly short-lived or are commonly embedded in other objects.

Similarly, Do not guidelines indicate something you should almost never do:

DO NOT assign instances of mutable types to read-only fields.

Less strong, Avoid guidelines indicate that something is generally not a good idea, but there are known cases where breaking the rule makes sense:

AVOID using

ICollection<T> or

ICollection as a parameter just to access the Count property.

Some more complex guidelines are followed with additional background information, illustrative code samples, and rationale:

DO implement

IEquatable<T> on value types. The

Object.Equals method on value types causes boxing and its default implementation is not very efficient because it uses reflection.

IEquatable<T>.Equals can offer much better performance and can be implemented so it does not cause boxing.

public struct Int32 : IEquatable{
public bool Equals(Int32 other){ ... }
}

Language Choice and Code Examples

One of the goals of the Common Language Runtime is to support a variety of programming languages: those provided by Microsoft, such as C++, VB, and C#, as well as third-party languages such as Eiffel, COBOL, Python, and others. Therefore, this book was written to be applicable to a broad set of languages that can be used to develop and consume modern frameworks. To reinforce the message of multilanguage framework design, we considered writing code examples using several different programming languages. However, we decided against this. We felt that using different languages would help to carry the philosophical message, but it could force readers to learn several new languages, which is not the objective of this book.

We decided to choose a single language that is most likely to be readable to the broadest range of developers. We picked C#, because it is a simple language from the C family of languages (C, C++, Java, and C#), a family with a rich history in framework development.

Choice of language is close to the hearts of many developers, and we offer apologies to those who are uncomfortable with our choice.

About This Book This book offers guidelines for framework design from the top down.

Chapter 1 is a brief introduction to the book, describing the general philosophy of framework design. This is the only chapter without guidelines.

Chapter 2, "Framework Design Fundamentals," offers principles and guidelines that are fundamental to overall framework design.

Chapter 3, "Naming Guidelines," contains naming guidelines for various parts of a framework, such as namespaces, types, members, and common design idioms.

Chapter 4, "Type Design Guidelines," provides guidelines for the general design of types.

Chapter 5,"Member Design," takes it a step further and presents guidelines for the design of members of types. Chapter 6, "Designing for Extensibility," presents issues and guidelines that are important to ensure appropriate extensibility in your framework.

Chapter 7, "Exceptions," presents guidelines for working with exceptions, the preferred error reporting mechanisms.

Chapter 8, "Usage Guidelines," contains guidelines for extending and using types that commonly appear in frameworks.

Chapter 9, "Common Design Patterns," offers guidelines and examples of common framework design patterns.

Appendix A contains a short description of coding conventions used in this book. Appendix B describes a tool called FxCop. The tool can be used to analyze framework binaries for compliance with the guidelines described in this book. A link to the tool is included on the DVD that accompanies this book.

Appendix C is an example of an API specification that framework designers within Microsoft create when designing APIs.

Included with the book is a DVD that contains several hours of video presentations covering topics presented in this book by the authors, a sample API specification, and other useful resources.

1.Always might be a bit too strong a word. There are guidelines that should literally be always followed, but they are extremely rare. On the other hand, you probably need to have a really unusual case for breaking a "Do" guideline and still have it be beneficial to the users of the framework.

Meet the Author

Brad Abrams was a founding member of the Common Language Runtime and .NET Framework teams at Microsoft Corporation. He has been designing parts of the .NET Framework since 1998 and is currently Group Program Manager of the .NET Framework team. Brad started his framework design career building the Base Class Library (BCL) that ships as a core part of the .NET Framework. Brad was also the lead editor on the Common Language Specification (CLS), the .NET Framework Design Guidelines, and the libraries in the ECMA\ISO CLI Standard. Brad has authored and coauthored multiple publications, including Programming in the .NET Environment and .NET Framework Standard Library Annotated Reference, Volumes 1 and 2. Brad graduated from North Carolina State University with a B.S. in computer science. You can find his most recent musings on his blog at http://blogs.msdn.com/BradA.

 

Krzysztof Cwalina is a program manager on the .NET Framework team at Microsoft. He was a founding member of the .NET Framework team and throughout his career has designed many .NET Framework APIs and framework development tools, such as FxCop. He is currently leading a companywide effort to develop, promote, and apply framework design and architectural guidelines to the .NET Framework. He is also leading the team responsible for delivering core .NET Framework APIs. Krzysztof graduated with a B.S. and an M.S. in computer science from the University of Iowa. You can find his blog at http://blogs.msdn.com/kcwalina.

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