Topic 15. Language-Integrated Query (LINQ)

Goal: become familiar with Language-Integrated Query (LINQ); learn to filter, sort, project, group, and join data using method syntax and query syntax, take deferred execution into account, use aggregate operators and the operators added in .NET 9–10, and create your own operators.

Lecture contents

1. LINQ fundamentals — What LINQ is · Method syntax and query syntax · Filtering, projection, and sorting
2. Execution and aggregation — Deferred and immediate execution · Elements, quantifiers, and aggregation
3. Grouping, joins, and how LINQ works — Grouping · Joins · Partitioning, set operations, and generation · How LINQ works inside
4. Examples and common mistakes — Example programs · Common mistakes

Practice and review

• Practice — 3 worked examples with complete code and output
• Tasks — 30 variants, each with tasks at three difficulty levels
• Summary — conclusions, self-check questions, and useful links