How do IOptions, IOptionsSnapshot, and IOptionsMonitor differ, and how would you validate critical settings before an ASP.NET Core API serves traffic?

IOptions, IOptionsSnapshot, IOptionsMonitor, and startup validation

Chooses the correct typed-options lifetime, validates required configuration early, and handles runtime changes deliberately.

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IOptions<T> provides one value for the application lifetime and works well for settings that are effectively fixed after startup. IOptionsSnapshot<T> is scoped and recomputes options once per request scope, while IOptionsMonitor<T> is singleton-friendly and can expose current values plus change notifications. I validate required settings with options validation and ValidateOnStart so a missing endpoint, invalid range, or malformed credential reference fails startup clearly instead of failing on the first request.

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Typed options, singleton and scoped consumption, per-request snapshots, change notifications, startup validation, named options, and safe reload behavior.

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Typed options turn configuration keys into an application contract. The choice of options interface controls when values are read and whether changes can appear while the process is running.
IOptions<T> provides one value for the application lifetime and works well for settings that are effectively fixed after startup. IOptionsSnapshot<T> is scoped and recomputes options once per request scope, while IOptionsMonitor<T> is singleton-friendly and can expose current values plus change notifications. I validate required settings with options validation and ValidateOnStart so a missing endpoint, invalid range, or malformed credential reference fails startup clearly instead of failing on the first request.
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Injecting IOptionsSnapshot into a singleton and crossing the scope boundary.
Binding typed settings but never validating required values or ranges.
Assuming every configuration provider supports live reload.
Doing slow or failure-prone reconstruction directly inside an OnChange callback.

How do IOptions, IOptionsSnapshot, and IOptionsMonitor differ, and how would you validate critical settings before an ASP.NET Core API serves traffic?

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