0 in a Nutshell The Definitive Reference Joseph Albahari C# 9.0 in a Nutshell by Joseph Albahari Copyright © 2021 Joseph Albahari. All rights reserved. Printed in the United States of America. Published by O’Reilly Media, Inc., 1005 Gravenstein Highway North, Sebastopol, CA 95472.
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Use of the information and instructions contained in this work is at your own risk. If any code samples or other technology this work contains or describes is subject to open source licenses or the intellectual property rights of others, it is your responsibility to ensure that your use thereof complies with such licenses and/or rights.0 represents the eighth major update to Microsoft’s flagship programming language, positioning C# as a language with unusual flexibility and breadth. At one end, it offers high-level abstractions such as query expressions and asynchronous continuations, whereas at the other end, it allows low-level efficiency through constructs such as custom value types and optional pointers. The price of this growth is that there’s more than ever to learn.
Although tools such as Microsoft’s IntelliSense—and online references—are excellent in helping you on the job, they presume an existing map of conceptual knowledge. This book provides exactly that map of knowledge in a concise and unified style—free of clutter and long introductions. Like the past six editions, C# 9.0 in a Nutshell is organized around concepts and use cases, making it friendly both to sequential reading and to random browsing. It also plumbs significant depths while assuming only basic background knowledge, making it accessible to intermediate as well as advanced readers.
This book covers C#, the Common Language Runtime (CLR), and the .NET 5 Base Class Library (BCL). We’ve chosen this focus to allow space for difficult and advanced topics without compromising depth or readability. Features recently added to C# are flagged so that you can also use this book as a reference for C# 8 and C# 7. Intended Audience This book targets intermediate to advanced audiences.
No prior knowledge of C# is required, but some general programming experience is necessary. For the beginner, this book complements, rather than replaces, a tutorial- style introduction to programming. This book is an ideal companion to any of the vast array of books that focus on an applied technology such as ASP.NET Core or Windows Presentation Foundation (WPF).0 in a Nutshell covers the areas of the language and .NET that such books omit, and vice versa. If you’re looking for a book that skims every .NET technology, this is not for you.
This book is also unsuitable if you want to learn about APIs specific to mobile device development. How This Book Is Organized Chapters 2 through 4 concentrate purely on C#, starting with the basics of syntax, types, and variables, and finishing with advanced topics such as unsafe code and preprocessor directives. If you’re new to the language, you should read these chapters sequentially. The remaining chapters focus on .NET 5’s Base Class Libraries, covering such topics as Language-Integrated Query (LINQ), XML, collections, concurrency, I/O and networking, memory management, reflection, dynamic programming, attributes, cryptography, and native interoperability.
You can read most of these chapters randomly, except for Chapters 5 and 6, which lay a foundation for subsequent topics. You’re also best off reading the three chapters on LINQ in sequence, and some chapters assume some knowledge of concurrency, which we cover in Chapter 14. What You Need to Use This Book The examples in this book require. You will also find Microsoft’s .NET documentation useful to look up individual types and members (which is available online).
Although it’s possible to write source code in Notepad and build your program from the command line, you’ll be much more productive with a code scratchpad for instantly testing code snippets, plus an integrated development environment (IDE) for producing executables and libraries. For a Windows code scratchpad, download LINQPad 6 from www. LINQPad fully supports C# 9.0 and is maintained by one of the authors. For a Windows IDE, download Visual Studio 2019: any edition is suitable for what’s taught in this book.
For a cross-platform IDE, download Visual Studio Code. NOTE All code listings for all chapters are available as interactive (editable) LINQPad samples. You can download the entire lot in a single click: at the bottom left, click the LINQPad’s Samples tab, click “Download more samples,” and then choose “C# 9.” Conventions Used in This Book The book uses basic UML notation to illustrate relationships between types, as shown in Figure P-1. A slanted rectangle means an abstract class; a circle means an interface.
A line with a hollow triangle denotes inheritance, with the triangle pointing to the base type. A line with an arrow denotes a one- way association; a line without an arrow denotes a two-way association. Sample diagram The following typographical conventions are used in this book: Italic Indicates new terms, URIs, filenames, and directories Constant width Indicates C# code, keywords and identifiers, and program output Constant width bold Shows a highlighted section of code Constant width italic Shows text that should be replaced with user-supplied values NOTE This element signifies a general note. WARNING This element indicates a warning or caution.
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Acknowledgments As always, it’s been an honor to have superb technical reviewers on the team. I’d like to extend particular thanks to Fred Silberberg and Stephen Toub from Microsoft for providing invaluable feedback at a busy time. The book was built on previous editions, whose technical reviewers I owe a similar honor: in recent editions, Vitek Karas, Stephen Toub, Paulo Morgado, Aaron Robinson, Jan Vorlicek, Sam Gentile, Rod Stephens, Jared Parsons, Matthew Groves, Dixin Yan, Lee Coward, Bonnie DeWitt, Wonseok Chae, Lori Lalonde, and James Montemagno. And previously, Eric Lippert, Jon Skeet, Stephen Toub, Nicholas Paldino, Chris Burrows, Shawn Farkas, Brian Grunkemeyer, Maoni Stephens, David DeWinter, Mike Barnett, Melitta Andersen, Mitch Wheat, Brian Peek, Krzysztof Cwalina, Matt Warren, Joel Pobar, Glyn Griffiths, Ion Vasilian, Brad Abrams, and Adam Nathan.
I appreciate that many of the technical reviewers are accomplished individuals at Microsoft, and I particularly thank you for taking the time to raise this book to the next quality bar. I want to thank Ben Albahari and Eric Johannsen, who contributed to previous editions, and the O’Reilly team—particularly my efficient and responsive editor Corbin Collins. Finally, my deepest thanks to my wonderful wife, Li Albahari, whose presence kept me happy throughout the project.NET C# is a general-purpose, type-safe, object-oriented programming language. The goal of the language is programmer productivity.
To this end, C# balances simplicity, expressiveness, and performance. The chief architect of the language since its first version is Anders Hejlsberg (creator of Turbo Pascal and architect of Delphi). The C# language is platform neutral and works with a range of platform-specific runtimes. Object Orientation C# is a rich implementation of the object-orientation paradigm, which includes encapsulation, inheritance, and polymorphism.
Encapsulation means creating a boundary around an object to separate its external (public) behavior from its internal (private) implementation details. Following are the distinctive features of C# from an object-oriented perspective: Unified type system The fundamental building block in C# is an encapsulated unit of data and functions called a type. C# has a unified type system in which all types ultimately share a common base type. This means that all types, whether they represent business objects or are primitive types such as numbers, share the same basic functionality.
For example, an instance of any type can be converted to a string by calling its ToString method. Classes and interfaces In a traditional object-oriented paradigm, the only kind of type is a class. In C#, there are several other kinds of types, one of which is an interface. An interface is like a class that cannot hold data.
This means that it can define only behavior (and not state), which allows for multiple inheritance as well as a separation between specification and implementation. Properties, methods, and events In the pure object-oriented paradigm, all functions are methods. In C#, methods are only one kind of function member, which also includes properties and events (there are others, too). Properties are function members that encapsulate a piece of an object’s state, such as a button’s color or a label’s text.
Events are function members that simplify acting on object state changes. Although C# is primarily an object-oriented language, it also borrows from the functional programming paradigm, specifically: Functions can be treated as values Using delegates, C# allows functions to be passed as values to and from other functions.