Joseph Albahari - C# 9.0 in a Nutshell

by Joseph Albahari

Copyright 2021 Joseph Albahari. All rights reserved.

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• March 2021: First Edition

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C# 9.0 represents the eighth major update to Microsofts 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 theres more than ever to learn. Although tools such as Microsofts IntelliSenseand online referencesare 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 stylefree 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). Weve 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). C# 9.0 in a Nutshell covers the areas of the language and .NET that such books omit, and vice versa.

If youre 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

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 youre new to the language, you should read these Chapters sequentially.

The remaining Chapters focus on .NET 5s 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 .

What You Need to Use This Book

The examples in this book require .NET 5. You will also find Microsofts .NET documentation useful to look up individual types and members (which is available online).

Although its possible to write source code in Notepad and build your program from the command line, youll 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.net (free). 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 whats 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 LINQPads Samples tab, click Download more samples, and then choose C# 9.0 in a Nutshell.

Conventions Used in This Book

The book uses basic UML notation to illustrate relationships between types, as shown in . 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.

Figure P-1. Sample diagram

The following typographical conventions are used in this book:

ItalicIndicates new terms, URIs, filenames, and directoriesConstant widthIndicates C# code, keywords and identifiers, and program outputConstant width boldShows a highlighted section of codeConstant width italicShows text that should be replaced with user-supplied values

Using Code Examples

This book is here to help you get your job done. In general, you may use the code in this book in your programs and documentation. You do not need to contact us for permission unless youre reproducing a significant portion of the code. For example, writing a program that uses several chunks of code from this book does not require permission. Selling or distributing examples from OReilly books does require permission. Answering a question by citing this book and quoting example code does not require permission (although we appreciate attribution). Incorporating a significant amount of example code from this book into your products documentation