DKNet

Inspect service registrations before adding duplicates

Part of DKNet.Fw.Extensions. Use ServiceCollectionRegistrationExtensions and ServiceCollectionExtensions in the Microsoft.Extensions.DependencyInjection namespace.

using System;
using Microsoft.Extensions.DependencyInjection;

var services = new ServiceCollection();
if (!services.IsRegistered<IWorker>())
    services.AddSingleton<IWorker, Worker>();
Console.WriteLine(services.IsRegisteredWithImplementation<IWorker>(typeof(Worker))); // True
Console.WriteLine(services[0].IsImplementationOf<Worker>()); // True

public interface IWorker { }
public sealed class Worker : IWorker { }

IsRegistered<TService>() checks for any matching service type. IsRegisteredWithImplementation<TService>(Type) checks the exact service and implementation pair. These helpers inspect registrations and do not register or resolve services.

For a ServiceDescriptor, IsImplementationOf(Type) / IsImplementationOf<T>() compares either ServiceType or ImplementationType. IsKeyedImplementationOf(key, Type) / IsKeyedImplementationOf<T>(key) first checks IsKeyedService and reference identity of ServiceKey, then delegates to the same implementation check.

⚠️ Gotchas & limits

• Factory and instance registrations do not expose their concrete type through ImplementationType; exact implementation checks do not inspect them.
• Key matching uses ReferenceEquals, so equal values held in different key objects do not match.
• The keyed helper delegates to IsImplementationOf, which reads ImplementationType rather than KeyedImplementationType. A keyed registration can match its service type while returning false for its concrete keyed implementation.
• The checks do not provide synchronization around later mutations of the service collection.

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