ASP.NET Core interview questions

Middleware pipeline, DI lifetimes, configuration and options, minimal APIs, and hosting.

3 questions in .NET & C#.

The .NET platform and C#A 20-minute read on how the topic fits together, before the questions..NET and C# fundamentals58 short answers on one page, for revising rather than studying.

medium3

mediumCodingConcept

You kick off background work from a controller action and it throws once the response has gone out. What is happening?

Detached ASP.NET Core background work can fail after the response because the request scope is disposed. Copy required values, create a fresh service scope, and run tracked work through IHostedService, BackgroundService or a durable queue.

5 minmid, senior, staff

mediumConceptScenario

What are the three DI lifetimes in ASP.NET Core, and what goes wrong when you inject a scoped service into a singleton?

ASP.NET Core DI lifetimes matter because a singleton that captures a scoped service turns per-request state into process-wide state. Captive dependencies cause stale data, threading bugs and disposed object failures.

4 minmid, senior

mediumScenarioConcept

You added an authorisation policy to an ASP.NET Core endpoint and it is not being enforced. Where do you look?

The pipeline is an ordered list you assembled, and authorisation cannot decide anything before routing has selected an endpoint to decide about. Registered in the wrong order it either runs against nothing or never runs at all, and neither produces an error - the request simply succeeds.

4 minmid, senior