2026

C# Interview Questions 2026

A current, 2026 snapshot of the C# interview questions worth knowing — kept up to date as frameworks and best practices evolve, so you prepare with what companies are actually asking in 2026.

60Questions14Beginner13Intermediate33Senior

60 C# questions

  1. 1Predicate vs Func vs Action delegatesIntermediate
  2. 2Exception Handling: Best Practices for Enterprise AppsIntermediate
  3. 3Task vs Thread: Resource ManagementIntermediate
  4. 4Dependency Injection Lifetimes: Transient, Scoped, SingletonIntermediate
  5. 5Generics: Constraints and Type SafetyIntermediate
  6. 6Extension Methods: Rules and Best PracticesIntermediate
  7. 7LINQ Deferred Execution and Immediate ExecutionIntermediate
  8. 8Delegates vs Events: Architecture and ImplementationIntermediate
  9. 9IEnumerable vs IQueryable: Performance and Use CasesIntermediate
  10. 10How async and await work internallyIntermediate
  11. 11The role of Constructors and DestructorsBeginner
  12. 12Difference between String and StringBuilder performanceBeginner
  13. 13What is the Managed Code and the CLR?Beginner
  14. 14Interface vs Abstract Class: When to use which?Beginner
  15. 15Understanding Access Modifiers in C#Beginner
  16. 16Difference between 'ref' and 'out' parametersBeginner
  17. 17The purpose of IDisposable and the 'using' statementBeginner
  18. 18What is Boxing and Unboxing with memory impactBeginner
  19. 19Explain the Stack and the Heap memory in C#Beginner
  20. 20Difference between Value Types and Reference TypesBeginner
  21. 21C# Interview Question 2 (Free)Intermediate
  22. 22C# Interview Question 5 (Free)Intermediate
  23. 23C# Interview Question 4 (Free)Beginner
  24. 24C# Interview Question 3 (Free)Senior
  25. 25C# Interview Question 1 (Free)Beginner
  26. 26Memory Barriers and Volatile keyword in Multi-threadingSenior
  27. 27Bit-manipulation and Binary primitives for low-level C#Senior
  28. 28Custom TaskSchedulers for specialized execution modelsSenior
  29. 29Designing Multi-tenant Database Providers in Entity FrameworkSenior
  30. 30Proximity Placement Groups and Network Latency in C# appsSenior
  31. 31Optimizing JSON Serialization: System.Text.Json internalsSenior
  32. 32The CRTP (Curiously Recurring Template Pattern) in C#Senior
  33. 33Middleware Architecture in ASP.NET Core internalsSenior
  34. 34Backpressure handling in Asynchronous StreamsSenior
  35. 35Native AOT: Benefits and Limitations for MicroservicesSenior
  36. 36The IDisposable Pattern and SafeHandle implementationSenior
  37. 37Channels (System.Threading.Channels) for Producer-Consumer patternsSenior
  38. 38SIMD (Single Instruction Multiple Data) in .NET performanceSenior
  39. 39Tiered Compilation and JIT Optimization layersSenior
  40. 40Preventing Closures and Capturing Variables memory leaksSenior
  41. 41Record types and Value-based Equality in C# 9.0+Senior
  42. 42Locking Mechanisms: Monitor, Mutex, Semaphore, and ReaderWriterLockSenior
  43. 43Strongly Typed vs Dynamic: The DLR internalsSenior
  44. 44IAsyncEnumerable: Streaming data asynchronouslySenior
  45. 45C# 9+ Source Generators: Compilers and Code GenerationSenior
  46. 46Understanding the 'yield' keyword and State State machinesSenior
  47. 47Memory Management: Pinned Object Heap (POH) explainedSenior
  48. 48ValueTask vs Task: Micro-optimization for High ThroughputSenior
  49. 49Implementing Thread-Safe Singletons with Lazy<T>Senior
  50. 50Covariance and Contravariance in GenericsSenior
  51. 51Reflection vs Expression Trees: Performance Trade-offsSenior
  52. 52The Liskov Substitution Principle in C# System DesignSenior
  53. 53Internals of the Async State MachineSenior
  54. 54Span<T> and Memory<T>: Low-allocation Memory AccessSenior
  55. 55Garbage Collection Generations and LOH Internal LogicSenior
  56. 56C# Advanced Interview Question 10Beginner
  57. 57C# Advanced Interview Question 9Senior
  58. 58C# Advanced Interview Question 8Intermediate
  59. 59C# Advanced Interview Question 7Beginner
  60. 60C# Advanced Interview Question 6Senior

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Frequently asked questions

Are these C# interview questions up to date for 2026?

Yes. This page reflects 60 C# interview questions kept current with today's frameworks, tooling and interview trends, with each answer maintained and dated.

What C# topics should I focus on in 2026?

Prioritise the fundamentals plus the modern patterns interviewers ask about now. Each question here includes a detailed answer, code example and common mistakes so you can target the highest-impact areas.

Are these questions free?

You can read the question and a short answer for free. A subscription unlocks the full detailed explanation, real-world example, common mistakes and follow-up questions for each one.