These 100 puzzles, with multiple levels of difficulty, can help you quickly improve your essential knowledge and problem solving skills in LINQ (Language-Integrated Query).

Master the functional programming style of LINQ for Object on immutable sequences. We focused on the fluent method notation. You'll find some query notation as well, but no LINQ for XML. We covered most if not all Enumerable standard query operators. Our strategy was to skip the trivial, avoid the clutter, but remember the basics and repeat what really matters.

We've split the content into 5 quizzes with 20 puzzles each. The puzzles are introduced as either coding problems with alternative possible solutions, or multiple-choice knowledge-related questions. In a separate section, all puzzles have detailed answers, explanations and references you can check after you first try to solve them with no hints.

More than 50 coding problems have one-click live C# source code you can run online and change as you wish. Dozens of problems are inspired from the most voted questions on Stack Overflow. Last quiz has problems asked in real Job Coding Technical Interviews, as described on LeetCode and elsewhere.

You must be already proficient in C# and comfortable with lambdas, extension methods and other advanced techniques. You must already know the basics of LINQ, as we don't teach LINQ here: these puzzles help you get better in LINQ.

The target audience starts with beginner C# developers and extends to expert C# programmers looking to test their skills. And have some fun in the process. Intermediate C# developers could better understand LINQ and its functional programming style.

We also target Software Engineers preparing for job coding interviews, or certification exams that require coding. LINQ is an essential component in solving complex algorithms and efficiently parsing data collections.

An interactive version of this book has been implemented on Udemy as "100 Interactive LINQ Puzzles".