C# and .NET Interview Questions Quiz (2026)

About this C# and .NET interview questions quiz

This free quiz turns the bool.dev series of 805 .NET interview questions and answers into 1,234 practice questions. Each question is tagged Junior, Middle or Senior, so you can prepare for the level you are interviewing for. After every answer you see a short explanation, the original answer from the article and what interviewers expect at that level.

How the quiz works

• Practice: choose topics and a level, then answer a run of 10, 20 or 50 questions. A correct first answer earns 3 stars, a correct second answer earns 1 star.
• Mock interview: choose 10 to 50 timed questions at Junior, Middle or Senior level, with one attempt each and a hiring verdict at the end.
• Visual explanations: about 300 questions show a diagram after you answer, covering SQL joins, indexes, garbage collection, the middleware pipeline, sagas, the outbox, circuit breakers, RAG, Kanban flow and more.
• Review mistakes: every question you miss comes back later until you answer it right three times in a row.
• Progress: XP ranks from Intern to Architect, streaks, badges and a coverage grid per topic and level, saved in your browser.

.NET interview topics covered

C# & .NET Fundamentals interview questions

106 quiz questions (35 Junior, 39 Middle, 32 Senior) based on Part 1: C# & .NET Fundamentals, which answers 49 questions in full. Sample questions:

• What is C#? How does it differ from languages like C or C++?
• NET Framework vs .NET Core vs .NET 5+: What You Need to Know?
• What is the Common Language Runtime (CLR)?
• What is the Common Type System (CTS)?

Types & Type Features interview questions

75 quiz questions (21 Junior, 32 Middle, 22 Senior) based on Part 2: Types & Type Features, which answers 35 questions in full. Sample questions:

• What is the purpose of the dynamic keyword in C#, and how does it differ from var?
• What are Tuples in C#, and what is their use case?
• How does the Span<T> type improve performance in C#?
• Explain the role of the default literal in C# and its use cases.

Collections & Data Structures interview questions

82 quiz questions (24 Junior, 37 Middle, 21 Senior) based on Part 3: Collections & Data Structures, which answers 39 questions in full. Sample questions:

• What Is Big O Notation, and Why Is It Important in C# Collections?
• Can you explain and compare the efficiency of .NET collections?
• Explain the difference between a one-dimensional and a multidimensional array in C#
• What are Inline Arrays in C# 12, and what advantages do they offer?

Async & Parallel interview questions

67 quiz questions (12 Junior, 30 Middle, 25 Senior) based on Part 4: Async & Parallel, which answers 32 questions in full. Sample questions:

• What is Runtime Async in .NET 11, and how does it differ from the traditional async/await implementation?
• What is the difference between asynchronous programming using async / await and traditional multithreading?
• What is the relationship between a Task and the .NET ThreadPool?
• How does the C# compiler transform an async method under the hood (state-machine generation, captured context, etc.)?

Design Patterns & Architecture interview questions

70 quiz questions (8 Junior, 33 Middle, 29 Senior) based on Part 5: Design Patterns & Architecture, which answers 34 questions in full. Sample questions:

• How do you detect and fix a God Object in a legacy .NET codebase?
• Explain YAGNI (“You Aren’t Gonna Need It”) with an example from your past projects.
• What’s the difference between DRY and the Single Responsibility Principle, and when might they conflict?
• How can Low Coupling and High Cohesion from GRASP be measured or evaluated in a C# class design?

ASP.NET Core interview questions

112 quiz questions (20 Junior, 54 Middle, 38 Senior) based on Part 6: ASP.NET Core, which answers 58 questions in full. Sample questions:

• What is ASP.NET Core, and how does it differ from the old ASP.NET (Framework)?
• What is Kestrel, and can ASP.NET Core run without IIS?
• How does the ASP.NET Core request processing pipeline work, and what is middleware?
• How do you create a custom middleware in ASP.NET Core?

SQL & EF Core interview questions

139 quiz questions (20 Junior, 72 Middle, 47 Senior) based on Part 7: SQL & EF Core, which answers 75 questions in full. Sample questions:

• What is normalization, and when would you denormalize your schema?
• How would you explain the ACID properties to a junior developer, and why are they important?
• What does SARGability mean in SQL?
• What’s the difference between a WHERE clause and a HAVING clause? Can you give a practical example of when you’d need HAVING?

NoSQL interview questions

122 quiz questions (10 Junior, 76 Middle, 36 Senior) based on Part 8: NoSQL, which answers 81 questions in full. Sample questions:

• What are the main categories of NoSQL databases?
• How do you decide between SQL and NoSQL for a new feature?
• What are common read/write patterns in NoSQL (GetByID, fan-out, time-series, append-only)?
• How do ACID and BASE principles differ in the context of NoSQL?

Microservices & Distributed interview questions

105 quiz questions (1 Junior, 81 Middle, 23 Senior) based on Part 9: Microservices & Distributed, which answers 81 questions in full. Sample questions:

• When does it make sense to isolate background processing into a separate microservice?
• How do you decide between a modular monolith and microservices?
• What is the Strangler Fig pattern, and how do you use it to migrate a legacy system?
• How do you define service boundaries using DDD Bounded Contexts?

Testing interview questions

75 quiz questions (4 Junior, 64 Middle, 7 Senior) based on Part 10: Testing, which answers 64 questions in full. Sample questions:

• What makes a test a “unit test” in C#, and what is usually mislabeled as unit?
• What do you test: behavior, state, or interactions, and why?
• Dummy vs Mock vs Stub vs Fake vs Spy: what is the difference, and when to use each?
• How do you avoid testing implementation details while still getting confidence?

Desktop interview questions

52 quiz questions (3 Junior, 45 Middle, 4 Senior) based on Part 11: Desktop, which answers 45 questions in full. Sample questions:

• What is WinUI 3, and how does it differ from UWP and WPF?
• How do you implement drag-and-drop between your desktop app and the OS in WinUI 3 or WPF?
• What is the Windows App SDK, and what problems does it solve over the classic Win32/UWP split?
• How does the WinUI 3 threading model work, and how do you marshal UI updates from background threads?

Mobile interview questions

59 quiz questions (55 Middle, 4 Senior) based on Part 12: Mobile, which answers 55 questions in full. Sample questions:

• How do native MAUI UI, BlazorWebView, HybridWebView, and WebView differ in 2026?
• How do you migrate a Xamarin.Forms app to .NET MAUI?
• How do .NET MAUI handlers differ from Xamarin.Forms renderers?
• How do you customize MAUI controls with handler mappers?

AI & LLMs interview questions

61 quiz questions (2 Junior, 47 Middle, 12 Senior) based on Part 13: AI & LLMs, which answers 48 questions in full. Sample questions:

• What is an LLM?
• What is the difference between traditional ML, LLMs, and generative AI, and where does each fit in a typical .NET product?
• What are tokens and context windows, and how do they constrain cost, latency, and prompt design in production?
• How do temperature and top-p interact, and why is true determinism still hard even at temperature 0?

Agile & Scrum interview questions

109 quiz questions (8 Junior, 101 Middle) based on Part 14: Agile & Scrum, which answers 109 questions in full. Sample questions:

• What is Agile, and how is it different from traditional Waterfall delivery?
• What are the core values and principles of the Agile Manifesto?
• What is the difference between Agile, Scrum, Kanban, and Lean?
• What problems does Agile try to solve in software delivery?

Frequently asked questions

How many .NET interview questions are in this quiz?

The quiz has 1,234 questions built from 805 C# and .NET interview questions and answers published on bool.dev, split across 14 topics.

Which levels does the quiz cover?

Every question is tagged Junior, Middle or Senior. You can practice one level or mix them, and the mock interview targets the level you choose.

Which topics are covered?

C# language and .NET runtime, types, collections, async and parallel programming, design patterns, ASP.NET Core, SQL and EF Core, NoSQL, microservices, testing, desktop, mobile with .NET MAUI, AI and LLMs, and Agile and Scrum.

What does the Review mistakes tab do?

It collects every question you answered wrong. Each one returns until you answer it right on the first try three times in a row, which is a simple form of spaced repetition.

Is my progress saved?

Yes. Progress, XP and your review deck are saved in your browser on this device. Nothing is sent to a server.