validation-patterns

Model validation in ASP.NET Core can be implemented using DataAnnotations, custom attributes, IValidatableObject, and FluentValidation. These mechanisms ensure data integrity by validating inputs during model binding and within application logic.

The best way to validate configuration in .NET is using the IValidateOptions<T> interface. This mechanism allows you to enforce rules on configuration settings during startup, ensuring invalid configurations fail fast before they impact application stability.

Yes, FluentValidation integrates seamlessly with MediatR pipeline behaviors. This combination centralizes application validation by automatically executing rules before requests reach handlers, separating validation logic from business logic cleanly.

Cross-field validation in C# is achieved using the IValidatableObject interface or FluentValidation rules. These approaches evaluate multiple properties simultaneously to enforce complex business rules that depend on the combined state of several fields.

Use custom validation attributes when standard DataAnnotations cannot express your specific business rules. Custom attributes encapsulate reusable logic for fields like passwords or emails, while DataAnnotations handle common scenarios like required fields.

Yes, IValidateOptions validates app settings at startup. By implementing this interface, the application checks configuration values during initialization, immediately failing and preventing startup if required settings are missing or invalid.