Question 1

How do Minimal APIs differ from traditional Controllers in ASP.NET Core?

Accepted Answer

Minimal APIs map routes directly through lightweight Lambdas with less overhead and faster startup, while Controllers provide a traditional structure suited to large, complex projects.

Question 2

How does the Middleware Pipeline work in ASP.NET Core, and why is registration order critical?

Accepted Answer

Each middleware runs code before calling next(), then waits for the response to return; order matters because UseAuthentication must come before UseAuthorization.

Question 3

How was Kestrel designed to become one of the world's fastest web servers, and what is a Reverse Proxy?

Accepted Answer

Kestrel uses non-blocking I/O built on Socket Pipelines and MemoryPools; it runs behind a Reverse Proxy (such as Nginx or IIS) for security and SSL management.

Question 4

What are the five ASP.NET Core Controller Filter stages, and in what order do they run?

Accepted Answer

The order is Authorization Filters, Resource Filters, Action Filters, Exception Filters, and finally Result Filters.

Question 5

How does Model Binding work in ASP.NET Core, and how do [FromBody], [FromRoute], and [FromQuery] differ?

Accepted Answer

It extracts request data and converts it to strongly typed C# objects; [FromBody] reads JSON, [FromRoute] reads URL path values, and [FromQuery] reads query parameters.

Question 6

How do IOptions, IOptionsSnapshot, and IOptionsMonitor differ in the Options Pattern?

Accepted Answer

IOptions is a fixed Singleton, IOptionsSnapshot is recomputed for each HTTP request to support live updates, and IOptionsMonitor is a Singleton that receives file-change notifications without a request context.

Question 7

How do you apply the built-in Rate Limiting Middleware in .NET 7+?

Accepted Answer

Call builder.Services.AddRateLimiter, configure algorithms such as FixedWindow, SlidingWindow, or TokenBucket, and apply them with [EnableRateLimiting].

Question 8

What is the ProblemDetails standard (RFC 7807), and how do you enable it for ASP.NET Core errors?

Accepted Answer

It standardizes HTTP error responses as structured JSON; enable it with builder.Services.AddProblemDetails().

Question 9

How does Output Caching in .NET 7+ improve on the older Response Caching Middleware?

Accepted Answer

It stores complete responses in server memory or Redis, supports cache invalidation by Tags, and uses locking to prevent a Stampede; the older middleware handled only client headers.

Question 10

How do you run continuous background tasks with BackgroundService, and what are the risks of injecting Scoped services into it?

Accepted Answer

Inherit from BackgroundService and write the logic in ExecuteAsync(); Scoped services cannot be injected directly because the service is a Singleton, so create a scope manually with IServiceScopeFactory.