.NET and C# interview questions

PerfView or dotnet-trace shows allocations and GC pauses.

IHostApplicationLifetime CancellationToken stops accepting work

Store hashed keys, rotate them, bind to scopes, and rate limit.

MediatR helps decouple handlers and cross-cutting behaviors.

EF.CompileQuery caches the translation for hot paths.

High-throughput network parsers benefit from Pipelines buffer management.

Microsoft.FeatureManagement or LaunchDarkly-style services toggle code paths.

I never log tokens, passwords, or full connection strings.

NetTopologySuite with EF spatial providers stores points and polygons.

Rolling updates with health checks, backward-compatible migrations, and dual-run periods.

Rent a buffer, use only the counted slice, and return in finally.

INumber and friends let algorithms work across numeric types.

I emit CSP headers via middleware with nonces for scripts.

A central identity provider issues tokens all APIs validate with the same authority.

The runtime starts with quick JIT then recompiles hot methods more optimally.

TPH uses a discriminator column in one table

Clients send an Idempotency-Key

Dump analysis, event counters, and looking for growing caches or event handlers.

Domain at the center, application use cases, infrastructure outside, API as entry.

Validate issuer, audience, lifetime, and signing key.