C# (.NET) Interview: 200 Questions and Answers

The book "C# (.NET) Interview: 200 Questions and Answers" is a practical guide created specifically for developers preparing for a technical interview. The author has collected and systematized the most common and complex questions asked at interviews in companies of various levels — from startups to large corporations.

Unlike dry reference books, this book is built on the "question-answer" principle: each section begins with a specific task or topic, followed by a detailed explanation with code examples and clarifications. This format allows you not just to memorize the correct answer, but also to understand the underlying logic of the .NET platform and the C# language.

Who is this book for?

• Junior developers — will learn which topics are most often asked and how to formulate answers correctly.
• Middle developers — will systematize their knowledge and fill gaps in complex topics (e.g., garbage collector operation or multithreading).
• Team Leads and Seniors — can use the book as a checklist for evaluating candidates or for preparing for an architect position interview.

What will you learn from the book?

• Data types, boxing/unboxing, structures and classes — how memory works in .NET.
• OOP in C#: inheritance, polymorphism, interfaces, abstract classes.
• Exceptions and error handling — try-catch-finally, custom exceptions.
• LINQ and collections: from basic queries to performance optimization.
• Asynchronous programming: async/await, Task, CancellationToken, IAsyncEnumerable.
• Multithreading and parallelism: lock, Monitor, Semaphore, Concurrent collections.
• Garbage Collection (GC) and memory management: generations, finalization, IDisposable.
• ASP.NET Core: Middleware, DI, controllers, minimal APIs, authentication.
• Entity Framework Core: Lazy Loading, N+1 problem, migrations, query optimization.
• Security: XSS, CSRF, SQL injection, working with tokens.

Each answer is accompanied not only by a textual explanation but also by code snippets that can be run immediately in Visual Studio or Rider. At the end of the book, there is a section with "pitfalls" — typical mistakes candidates make and tips on how to avoid them.

The book is written in a lively, understandable language, without excessive academicism. It is suitable both for intensive preparation a few days before an interview and for systematic study over a month.

Important: the material is focused on .NET 6/7/8 and is relevant for the modern technology stack. All examples have been tested on real projects and comply with the best practices of 2024–2025.

If you want to feel confident in an interview, clearly answer questions about C# and .NET, and make an impression on the interviewer — this book will be your reliable assistant.