Architecture C# active any

Dependency injection is validated early

csharp-arch-003

Intent

Container and lifetime mistakes should fail during startup or automated validation, not at the first production request.

Applicability

Applies to apps using Microsoft.Extensions.DependencyInjection.

What to inspect

Host-builder validation, BuildServiceProvider() misuse, singleton registrations, and lifetime-sensitive constructor dependencies.

Pass criteria

Startup validation is enabled or equivalent host-building tests exist, and singleton registrations do not pull scoped-only abstractions such as IOptionsSnapshot<T>.

Fail criteria

The diff disables validation, builds secondary root providers in registration code, or wires a singleton to scoped-only DI abstractions.

Do not flag

Library extension methods and test-only host construction.

Confidence guidance

HIGH when validation is bypassed or the lifetime mismatch is direct. MEDIUM when startup wiring is partly inferred. LOW when the host path is out of scope.

Remediation

Enable provider validation, remove secondary roots, and fix lifetime mismatches.

Pass example

builder.Host.UseDefaultServiceProvider(o => { o.ValidateScopes = true; o.ValidateOnBuild = true; });

Fail example

builder.Services.AddSingleton<CachePrimer>(); // CachePrimer(IOptionsSnapshot<CacheOptions> options)