Introduction

By the time you are holding this book in your hands, I will have 30 years in since the first time I wrote some code. That code was ROM-BASIC on a TRS-80 in Washington grammar school in Owosso, Michigan, and I was in the fifth grade. Making the “tank” slide back and forth shooting blips across the screen was neat. Changing the code to change blip speeds and numbers of targets was exhilarating. Three decades later and I get more excited each passing year. There are great technologies on the horizon like Microsoft Surface, Popfly, and LINQ. This book is about LINQ, or Language INtegrated Query.

LINQ is a SQL-like language for C#. When I first saw it, I didn’t like it. My first impression was that someone had glommed on a bastardization of C# and it was ugly like SQL can get. I didn’t like it because I didn’t understand it. However, I gave LINQ a second chance (as I want you to do) and discovered that LINQ is thoroughly integrated, tremendously powerful, and almost as much fun as a Tesla Roadster or doing hammerheads in an Extra 300L.

The query capabilities of LINQ are extended to objects, SQL, DataSets, XML, XSD, entities, and can be extended to other providers like Active Directory or SharePoint. This means that you can write queries—that are similar in syntax—against objects, data, XML, XSD, entities, or Active Directory (with a little work) much like you would a SQL query in a database. And, LINQ is actually engineered artfully and brilliantly on top of generics as well as some new features in .NET 3.5, such as extension methods, anonymous types, and Lambda Expressions. Another very important characteristic of LINQ is that it clearly demonstrates Microsoft’s willingness to innovate and take the best of existing technologies like Lambda Calculus—invented in the 1930s—and if it’s good or great, incorporate these elements into the tools and languages we love.

LINQ and its underpinnings are powerful and challenging, and in this book you will get what you need to know to completely understand all that makes LINQ work and begin using it immediately. You will learn about anonymous methods, extension methods, Lambda Expressions, state machines, how generics and the CodeDOM play a big role in powerful tools like LINQ, and writing LINQ queries and why you will want to do it in the bigger, grander scheme of things. You will also learn how to save a ton of time and effort by not hard-coding those elements that you will no longer need or want to hard-code, and you will have a better grasp of how LINQ fits into n-tier architectures without breaking guidelines that have helped you succeed to date.

Brought to you by a four-time Microsoft MVP and columnist for over a decade, LINQ Unleashed for C# will teach you everything you need to know about LINQ and .NET 3.5 features and how to be more productive and have more fun than ever before.

Conventions Used in This Book

The following typographic conventions are used in this book:

Code lines, commands, statements, variables, and text you see onscreen appear in a monospace typeface.

Occasionally in listings bold is used to draw attention to the snippet of code being discussed.

Placeholders in syntax descriptions appear in an italic monospace typeface. You replace the placeholder with the actual filename, parameter, or whatever element it represents.

Italics highlight technical terms when they’re being defined.

A code-continuation icon is used before a line of code that is really a continuation of the preceding line. Sometimes a line of code is too long to fit as a single line on the page. If you see → before a line of code, remember that it’s part of the line immediately above it.

The book also contains Notes, Tips, and Cautions to help you spot important or useful information more quickly.