microsoft-extensions-configuration

The Problem: Applications often fail at runtime due to misconfiguration - missing connection strings, invalid URLs, out-of-range values. These failures happen deep in business logic, far from where configuration is loaded, making debugging difficult.

The Solution: Validate configuration at startup. If configuration is invalid, the application fails immediately with a clear error message. This is the "fail fast" principle.

Key Point: .ValidateOnStart() is critical. Without it, validation only runs when the options are first accessed, which could be minutes or hours into application runtime.

Microsoft.Extensions.Options patterns including IValidateOptions, strongly-typed settings, validation on startup, and the Options pattern for clean configuration management. Source: foxminchan/bookworm.