Professional C# and .NET, 2021st Edition

9Language Integrated Query

WHAT'S IN THIS CHAPTER?

• Working with traditional queries across objects using List
• Using extension methods
• Getting to know LINQ query operators
• Working with Parallel LINQ
• Working with expression trees

CODE DOWNLOADS FOR THIS CHAPTER

The source code for this chapter is available on the book page at www.wiley.com. Click the Downloads link. The code can also be found at https://github.com/ProfessionalCSharp/ProfessionalCSharp2021 in the directory 1_CS/LINQ.

The code for this chapter is divided into the following major examples:

• LINQIntro
• EnumerableSample
• ParallelLINQ
• ExpressionTrees

All the sample projects have nullable reference types configured.

LINQ OVERVIEW

Language Integrated Query (LINQ) integrates query syntax inside the C# programming language, making it possible to access different data sources with the same syntax. LINQ accomplishes this by offering an abstraction layer.

This chapter describes the core principles of LINQ and the language extensions for C# that make the C# LINQ query possible.

NOTE For details about using LINQ across a database, read Chapter 21, “Entity Framework Core.”

This chapter starts with a simple LINQ query before diving into the full potential of LINQ. The C# language offers an integrated query language that is converted to method calls. This section shows you what the conversion looks like so you can use all the possibilities of LINQ.

Lists and Entities

The LINQ queries in this chapter are ...