CODEWITHSUNDEEP
c#autofac
rbr94
rbr94

Reputation: 2277

Autofac: Resolve Lists with only one element fails

1. Case:

Registrations:

var builder = new ContainerBuilder();

builder.RegisterType<ExportSchedule>()
       .As<ISchedule>()
       .InstancePerLifetimeScope();

builder.RegisterType<ImportReferenceDataSchedule>()
       .As<ISchedule>()
       .InstancePerLifetimeScope();

Resolving for BaseconfigScheduleHandler class:

public BaseConfigScheduleHandler(List<ISchedule> schedules) {
    this.Schedules = schedules;
}

public List<ISchedule> Schedules { get; }

This case works fine. I got both registered instances of ISchedule.

2. Case

I change the registrations to only register 1 element:

var builder = new ContainerBuilder();

builder.RegisterType<ExportSchedule>()
       .As<ISchedule>()
       .InstancePerLifetimeScope();

In this case the dependency resolution fails with following exception:

Autofac.Core.DependencyResolutionException : An error occurred during the activation of a particular registration. See the inner exception for details. Registration: Activator = BaseConfigScheduleHandler (ReflectionActivator), Services = [docXtrans.TuevApi.Core.Data.Service.IScheduleHandler], Lifetime = Autofac.Core.Lifetime.CurrentScopeLifetime, Sharing = Shared, Ownership = OwnedByLifetimeScope ---> None of the constructors found with 'Autofac.Core.Activators.Reflection.DefaultConstructorFinder' on type 'docXtrans.TuevApi.Core.Data.Service.BaseConfigScheduleHandler' can be invoked with the available services and parameters: Cannot resolve parameter 'System.Collections.Generic.List1[ISchedule] schedules' of constructor 'Void .ctor(System.Collections.Generic.List1[BaseConfigSchedule], System.Collections.Generic.List`1[ISchedule])'. (See inner exception for details.)

I need both cases and want to be flexible having 1 or more elements in this collection. How can I solve that problem?

Upvotes: 0

Views: 191

Answers (1)

mjwills
mjwills

Reputation: 23819

I'd suggest using one of the supported enumeration types. As per the docs:

Enumeration (IEnumerable, IList, ICollection)

In your case, that could be:

IEnumerable<ISchedule> schedules

Upvotes: 1

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