Validating configuration (e.g., using IValidateOptions)?

Short answer: You can validate bound config using IValidateOptions<T>: public class MySettingsValidator : IValidateOptions<MySettings> {

Example code

public ValidateOptionsResult Validate(string name, MySettings options) { if (string.IsNullOrWhiteSpace(options.ApiKey)) {
return ValidateOptionsResult.Fail("ApiKey is required."); }
return ValidateOptionsResult.Success;
}
} Register with DI: services.AddSingleton<IValidateOptions<MySettings>, MySettingsValidator>();

Real-world example (ShopNest)

A ShopNest checkout request flows through middleware, hits a minimal API or controller, uses scoped services, and returns ProblemDetails on errors.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.