ASP.NET Core Interview Questions and Answers

ASP.NET Core interview questions — the request pipeline and middleware, built-in dependency injection, configuration, hosting, Kestrel, Web API and EF Core integration.

Start with the top questions Browse all questions

ASP.NET Core

49Questions

12Topics

Basic to AdvancedDifficulty

Fresher to 5+ YrsExperience

All ASP.NET Core Questions (49) Sort by

01 How does configuration work in ASP.NET Core? Configuration is built from an ordered set of providers — appsettings.json, appsettings.{Environment}.json, user… Configuration Basic 1–2 Yrs
02 What is the Options pattern, and what is the difference between IOptions, IOptionsSnapshot and IOptionsMonitor? The Options pattern binds a configuration section to a strongly typed class and injects it. IOptions<T> — singleton,… Configuration Intermediate 2–3 Yrs
03 What are environments in ASP.NET Core? An environment is a named runtime context — Development, Staging, Production (or your own) — set by the… Configuration Basic Fresher
04 What is a hosted service / BackgroundService in ASP.NET Core? IHostedService (usually via the BackgroundService base class) runs background work tied to the app's lifetime — queue… Hosting Intermediate 2–3 Yrs
05 What are Minimal APIs, and how do they compare to controllers? Minimal APIs define HTTP endpoints as lambdas directly on the app — app.MapGet("/orders/{id}", (int id, IOrderService… Web API Intermediate 2–3 Yrs
06 How do you register and resolve multiple implementations of the same interface in ASP.NET Core DI? Register each implementation against the interface; the container collects them. Inject IEnumerable<INotifier> to get… Dependency Injection Advanced 3–5 Yrs
07 What is the difference between authentication and authorization in ASP.NET Core? Authentication establishes who the caller is — it validates a cookie, JWT or other credential and builds a… Authentication Basic 1–2 Yrs
08 What is JWT authentication and how does it work? A JWT is a signed token with three base64url parts — header, payload (claims), signature. After login the server… Authentication Intermediate 2–3 Yrs
09 What is IHttpClientFactory and why should you use it? IHttpClientFactory manages the lifetime of HttpClient's underlying HttpMessageHandler, pooling and rotating them. It… Performance Intermediate 2–3 Yrs
10 What is the difference between response caching and output caching in ASP.NET Core? Response caching sets HTTP cache headers (Cache-Control) and honours them via a middleware cache — it relies on the… Performance Advanced 3–5 Yrs
11 What is model binding in ASP.NET Core, and what are the binding sources? Model binding maps values from the HTTP request onto your action's parameters. Sources: [FromRoute], [FromQuery],… Web API Basic 1–2 Yrs
12 What is the role of Program.cs (and the old Startup class) in ASP.NET Core? Program.cs is the application's entry point: it builds the host, registers services in the DI container… Fundamentals Basic Fresher
13 How does logging work in ASP.NET Core? Logging is built in: inject ILogger<T> and call _logger.LogInformation(...). It's provider-based — Console, Debug,… Logging Basic 1–2 Yrs
14 What is the difference between app.Use, app.Run and app.Map? app.Use adds middleware that can call next() to continue the pipeline (or not). app.Run adds a terminal middleware… Middleware Basic 1–2 Yrs
15 What is policy-based authorization, and how does it compare to role-based? Role-based ([Authorize(Roles = "Admin")]) checks a single claim value. Policy-based authorization names a rule… Authorization Intermediate 2–3 Yrs
16 How does rate limiting work in ASP.NET Core? The built-in rate limiter (.NET 7+) is middleware — AddRateLimiter + UseRateLimiter — with four algorithms: fixed… Performance Advanced 3–5 Yrs
17 What are health checks in ASP.NET Core? Health checks expose an endpoint (/health) that reports whether the app and its dependencies are working. Register… Hosting Intermediate 2–3 Yrs
18 What is the standard resilience handler / Polly, and what does it give you? Polly is a resilience library; AddStandardResilienceHandler() (Microsoft.Extensions.Http.Resilience) wires a sensible… Performance Advanced 3–5 Yrs
19 What is the middleware ordering rule, and what breaks if you get it wrong? Middleware runs in the order you add it, and the response unwinds in reverse. The rules that matter: exception… Middleware Intermediate 2–3 Yrs
20 What is the difference between AddControllers, AddControllersWithViews, AddRazorPages and AddMvc? AddControllers() — controllers + API features only (for a Web API). AddControllersWithViews() — adds Razor views and… Fundamentals Basic 1–2 Yrs
21 What is HttpContext, and why shouldn't you store or use it outside a request? HttpContext holds everything about the current request/response — User, Request, Response, Items, request services.… Fundamentals Advanced 3–5 Yrs
22 How do you configure JSON serialization in ASP.NET Core (System.Text.Json)? ASP.NET Core uses System.Text.Json by default. Configure it with AddControllers().AddJsonOptions(o => { ... }) —… Web API Intermediate 2–3 Yrs
23 Why can't you inject a scoped service into the constructor of custom middleware? Conventional middleware is instantiated once at startup (effectively a singleton), so injecting a scoped service like… Dependency Injection Advanced 3–5 Yrs
24 What is the generic host, and how does it differ from the web host? The generic host (IHost) provides DI, configuration, logging and a lifetime for any .NET app — including non-web… Hosting Advanced 3–5 Yrs
25 How do you handle CSRF / anti-forgery for a SPA calling an ASP.NET Core API? If the SPA authenticates with a bearer token in a header (not a cookie), classic CSRF doesn't apply — the browser… Authentication Advanced 3–5 Yrs
26 What lifetime should you register a repository, a service, and a cache? Repository / unit-of-work / anything touching DbContext → Scoped (matches the request-scoped context). Stateless… Dependency Injection Intermediate 2–3 Yrs
27 What is the difference between Data Annotations validation and FluentValidation? Data Annotations ([Required], [Range]) are attributes on the model — simple, built-in, run automatically.… Web API Intermediate 2–3 Yrs
28 How does ASP.NET Core serve static files, and how do you cache them? UseStaticFiles() serves files from wwwroot. Place it early in the pipeline (before routing/auth) so assets skip… Performance Basic 1–2 Yrs
29 What is the Options validation pattern, and why validate configuration on startup? Bind config to an options class and validate it:… Configuration Intermediate 2–3 Yrs
30 What is ASP.NET Core? ASP.NET Core is a free, open-source, cross-platform framework for building web apps, APIs and real-time services on… Fundamentals Basic Fresher
31 What is the difference between ASP.NET MVC and ASP.NET Core? ASP.NET MVC 5 runs only on the Windows .NET Framework, is hosted in IIS through System.Web, and needs third-party… Fundamentals Intermediate 2–3 Yrs
32 What is middleware in ASP.NET Core? Middleware is a component that sits in the request pipeline. Each piece of middleware receives the HttpContext, can do… Middleware Basic 1–2 Yrs
33 Explain the ASP.NET Core request pipeline. A request enters through Kestrel, is handed to the middleware pipeline as an HttpContext, and passes through each… Middleware Intermediate 2–3 Yrs
34 What is Kestrel in ASP.NET Core? Kestrel is the default, cross-platform web server built into ASP.NET Core. It is a fast, lightweight HTTP server that… Hosting Basic 1–2 Yrs
35 What is Dependency Injection in ASP.NET Core? Dependency Injection (DI) is a design technique where a class receives the objects it depends on from the outside —… Dependency Injection Intermediate 2–3 Yrs
36 What is loose coupling? Loose coupling means a class depends on what another component does (an abstraction) rather than how it does it (a… Dependency Injection Basic 1–2 Yrs
37 What is Inversion of Control (IoC)? Inversion of Control is a principle where the flow of control — who creates objects, who calls whom — is handed to a… Dependency Injection Intermediate 2–3 Yrs
38 What are service lifetimes in ASP.NET Core? A service lifetime controls how long the container keeps and reuses an instance. There are three: Transient — a new… Dependency Injection Intermediate 2–3 Yrs
39 What is the difference between Transient, Scoped and Singleton? Transient: new instance on every injection — most short-lived. Scoped: one instance per request, shared within that… Dependency Injection Intermediate 2–3 Yrs
40 Why is DbContext registered as Scoped? DbContext is registered as Scoped because it is a lightweight, stateful, not thread-safe unit-of-work. One instance… Dependency Injection Advanced 3–5 Yrs
41 What is a captive dependency? A captive dependency is when a longer-lived service holds a reference to a shorter-lived one, “capturing” it and… Dependency Injection Advanced 3–5 Yrs
42 How do you run background work in ASP.NET Core? Implement IHostedService, or more commonly inherit BackgroundService and override ExecuteAsync(CancellationToken… Hosting Intermediate 2–3 Yrs
43 What does it mean for a service to be stateless, and why does it matter? A stateless service keeps no client-specific data in its own memory between requests — everything needed is in the… Architecture Intermediate 2–3 Yrs
44 What is the difference between session-based auth and token-based auth? Session auth — the server creates a session, stores it server-side, and gives the client a session-id cookie; each… Authentication Intermediate 2–3 Yrs
45 A deployment has broken production. Walk me through what you do. Stabilise first, diagnose second. Confirm the blast radius, roll back to the last known-good version (or shift traffic… Scenario Advanced 3–5 Yrs
46 A read-heavy endpoint is hammering the database. How do you add caching safely? Confirm the data tolerates staleness and by how much. Pick the layer — output caching for whole responses, a… Scenario Advanced 3–5 Yrs
47 Your app depends on a third-party API that is slow and sometimes down. How do you make your app resilient? Wrap the calls with resilience policies: a sensible timeout, retries with backoff + jitter for transient failures, a… Scenario Advanced 3–5 Yrs
48 An API endpoint is fast in testing but slow under production load. How do you investigate? Reproduce with realistic concurrency, then use data — server metrics (CPU, memory, GC, thread-pool queue), request… Scenario Advanced 3–5 Yrs
49 You get an intermittent NullReferenceException in production that you can't reproduce locally. How do you approach it? Get the exact stack trace and a correlation ID from structured logging, and identify the line and the reference that's… Scenario Advanced 3–5 Yrs

About these ASP.NET Core questions

ASP.NET Core interviews centre on two things: the request pipeline and the built-in dependency injection container. If you can explain how middleware is ordered and short-circuited, and how AddTransient, AddScoped and AddSingleton differ (and why getting them wrong causes captive-dependency bugs), you have covered most of what a mid-level interview will probe.

From there, expect configuration and options, hosting and Kestrel, minimal APIs vs controllers, authentication/authorization, and how EF Core's DbContext fits the scoped lifetime. The Dependency Injection chain in this section walks the exact follow-up sequence many interviewers use.

ASP.NET Core Interview Questions and Answers

No questions match those filters

About these ASP.NET Core questions