microsoft-extensions-configuration

Validate appsettings at startup in .NET by binding configuration to strongly-typed classes and invoking ValidateOnStart() with Data Annotations or custom IValidateOptions to catch invalid settings before runtime.

The options pattern binds configuration from appsettings.json to C# classes, enabling strongly-typed settings access. It supports IOptionsSnapshot for scoped requests and IOptionsMonitor for change detection across the application lifecycle.

Implement IValidateOptions to perform complex settings validation in .NET. This allows custom logic for environment-aware checks, such as ensuring production database connection strings do not contain localhost.

Validators can leverage dependency injection in .NET to perform environment-aware or complex checks. This ensures configuration validation logic can access scoped services and runtime environment context during startup validation.

IOptionsSnapshot recomputes settings per request scope, while IOptionsMonitor provides real-time change notifications throughout the application lifecycle. Both support named options for managing multiple configuration sections simultaneously.

Apply post-configuration adjustments in .NET using IPostConfigureOptions to modify or enrich settings after initial binding. This ensures default values are applied or dependencies are resolved before the options are finalized.