.NET and C# interview questions

They let you write simple members with => instead of a block.

They return values from patterns cleanly and force exhaustive cases with warnings.

It streams async sequences with await foreach.

It avoids capturing the SynchronizationContext after await.

IQueryable can translate expressions to SQL via a provider.

I use Results.Problem or validation ProblemDetails for consistent error JSON.

It selects the endpoint first, then runs middleware that can see the chosen route.

I add CORS policy with allowed origins, methods, and headers, then UseCors.

It watches loaded entities for property changes and builds INSERT/UPDATE/DELETE on SaveChanges.

I mark a rowversion or token property and EF includes it in WHERE on update.

Identity hashes with a strong algorithm and salt via PasswordHasher.

It encrypts tokens, cookies, and antiforgery payloads with keys managed by the Data Protection API.

I reuse buffers with ArrayPool, avoid boxing, prefer spans, and cut LINQ in tight loops.

I log message templates with named placeholders so sinks index fields.

They generate C# at compile time from analyzers.

Endpoints report if DB and dependencies are healthy for orchestrators.

Owned types store related value objects in the same table or dependent table without their own identity key for domain use.

Response caching uses HTTP cache headers and middleware.

You write the business row and an outbox message in one transaction, then a relay publishes to the broker.

It is a high-performance producer/consumer queue for in-process async work.