Whether the job post says .NET interview questions, net interview questions, or .NET Core interview questions, this page is the map of that loop, not the page that answers one stack.
This guide is the question bank for that loop — topic tables, on-page sample answers with strong answer / red flag, and links to full scenario write-ups. It is not a 300-line MCQ dump.
Hub index: interview questions.
How to use these .NET interview questions
- Pick your level (mid vs staff)
- Rehearse the sample answers on this page out loud
- Open the linked article when you need the full scenario
- Read the how-to post when you need a merge checklist
.NET interview questions by topic
C# and async (most common mid-level loop)
| Question | Short answer | Full scenario |
|---|---|---|
Does async create a thread? | No for I/O — yields the worker | Async await interview questions |
.Result on ASP.NET Core? | Thread pool starvation, not UI deadlock | Thread pool starvation |
async void on a controller? | Unobserved exceptions — use Task | Async await interview questions |
WhenAll on one DbContext? | Race — not thread-safe | WhenAll vs Parallel |
Task vs Thread? | Promise vs OS worker | Task vs Thread |
ConfigureAwait(false) on API? | Library rule, not controller default | ConfigureAwait |
Definitions: asynchronous meaning, async vs sync.
ASP.NET Core / .NET Core interview questions
| Question | Short answer | Full scenario |
|---|---|---|
| Captive dependency? | Singleton captured scoped DbContext | ASP.NET Core scenarios |
| 401 vs 403? | Not authenticated vs forbidden | 401 vs 403 |
| Middleware order? | CORS, exception handling, auth, authz | Middleware order |
| JWT works in Postman, not Angular? | CORS, cookie vs bearer, clock skew | JWT auth |
| Why idle CPU and 504s? | Sync-over-async starving pool | Starvation |
.NET Core interview questions and ASP.NET Core Web API interview questions are the same panel under two names. Interviewers still say ".NET Core." Full narratives: ASP.NET Core interview questions scenarios.
C# interview questions and answers (staff / expert)
| Question | Short answer | Full scenario |
|---|---|---|
| Export 200k rows OOM? | IAsyncEnumerable, project in SQL | Expert interview questions |
| Multi-tenant cache leak? | Key must include tenantId | ConcurrentDictionary |
| Fire-and-forget email? | Channel + BackgroundService | BackgroundService async |
| Deadlock vs starvation? | UI sync context vs pool queue | Deadlock explained |
EF Core interview questions
| Question | Short answer | Full scenario |
|---|---|---|
| N+1? | Loop + lazy load or missing Include | EF interview questions |
| Include vs AsSplitQuery? | JOIN explosion vs multiple SQL | N+1 Include AsSplitQuery |
| Lost update vs deadlock? | RowVersion vs RCSI | Optimistic concurrency |
| Global query filter pitfall? | IgnoreQueryFilters for admin | EF interview questions |
| 1-1 / 1-n / n-n mapping? | Owned vs skip join vs join entity | EF Core relationships |
Angular + ASP.NET Core interview questions
| Question | Short answer | Full scenario |
|---|---|---|
| Refresh token race? | Queue 401s, single refresh | 401 refresh queue |
| JWT interceptor design? | Attach bearer, handle 401 | Angular JWT interceptors |
| Auth guard vs API? | Guard is UX; API enforces | Auth guard |
Full list: Angular interview questions.
Sample .NET interview questions and answers
Use this format in the room: symptom → cause → fix. Red flags are what junior dumps sound like.
Q: What is the difference between async and multithreading?
Strong answer: async/await frees the ThreadPool worker during I/O waits — the Task is a promise, not a dedicated thread. Multithreading runs work on multiple workers (Task.Run, Parallel, lock). On ASP.NET Core APIs, default to async for SQL and HTTP; use threading for CPU offload and in-memory gates.
Red flag: "Async creates a new thread for every call" or "always wrap DB calls in Task.Run."
Q: What is dependency injection in .NET?
Strong answer: Inversion of control — the container constructs services and injects them. Lifetimes matter: Singleton (one per app), Scoped (per request — DbContext), Transient (every resolve). Never inject scoped into singleton without an IServiceScopeFactory.
Red flag: Listing lifetimes without naming captive dependency or why DbContext is scoped.
Q: Captive dependency — what breaks in production?
Strong answer: A singleton service that holds a scoped DbContext (or other scoped dependency). Under load you see cross-request data leaks, disposed-context exceptions, or stale tenants. Fix: inject a factory, create a scope per operation, or demote the consumer to scoped.
Red flag: "Just make everything singleton" or "DbContext is fine as a singleton because EF is thread-safe" (it is not).
Q: 401 vs 403 on a Web API?
Strong answer: 401 — not authenticated (missing/invalid token). 403 — authenticated but not authorized. SPA interceptors that treat every 403 as "log out" create false logout storms.
Red flag: Using 401 for both missing login and missing permission.
Q: Repository pattern — yes or no?
Strong answer: DbContext is already a unit of work. Add repositories for named, reused queries — not generic IRepository<T> on every entity. Prefer query objects or application services when the "repository" is a thin wrapper over Set<T>().
Red flag: "Always wrap EF in a generic repository for Clean Architecture" with no named query examples. Details: repository definition.
Q: What is Clean Architecture in ASP.NET Core?
Strong answer: Domain and application rules at the center; infrastructure and UI at the edges. Controllers stay thin. Goal is testable boundaries — not copying folder templates without domain complexity. Clean Architecture guide.
Red flag: Equating Clean Architecture with "lots of folders" and no domain invariants.
Q: N+1 in EF Core — how do you prove it?
Strong answer: Loop that triggers lazy loads or missing Include/Select projections. Prove with SQL logging or a profiler (many round-trips). Fix with includes, split queries, or projecting only needed columns. EF Core interview questions.
Red flag: "Always use Include on every navigation" without talking about cartesian explosion or AsSplitQuery.
Net interview questions vs MCQs
Net questions, net test questions, and dot net MCQs belong on a screening quiz, not a senior panel. If you get them, map each tick-box to a scenario on this guide instead of memorizing a PDF.
Study order (recommended)
Week 1 — Async track
asynchronous meaning → async await interview questions → starvation how-to
Week 2 — ASP.NET Core / .NET Core track
ASP.NET Core scenarios → DI lifetimes → JWT + Angular interceptors
Week 3 — Data track
EF Core interview questions → relationships how-to → N+1 / AsSplitQuery
Week 4 — Staff polish
Expert interview questions → Channels, IAsyncEnumerable
If an interviewer asks
"What .NET interview questions should a senior know?"
Production failures: tenant cache leaks, starvation dumps, JWT rotation, EF concurrency, and API design tradeoffs — not keyword lists.
"ASP.NET Core vs .NET interview questions?"
.NET is the runtime and language. ASP.NET Core / Web API questions are web-specific: pipeline, auth, hosting, EF in request scope. ".NET Core" in a job spec almost always means that web loop, not Framework.
"Where should I start tonight?"
One async scenario + one captive-DI scenario + one EF concurrency scenario. Answer aloud, then open the linked full article.
All tracks: interview questions hub.