Question

I am using the following code for register:

builder.RegisterType<QCatVCardParser>().Named<IQCatParser>(".VCF");              
builder.RegisterType<QCatVCardParser>().Named<IQCatParser>(".VCARD");            
builder.RegisterType<QCatOutlookMessageParser>().Named<IQCatParser>(".MSG");
builder.RegisterType<QCatMimeMessageParser>().Named<IQCatParser>(".EML");
builder.RegisterType<QCatCalendarParser>().Named<IQCatParser>(".ICS");
container = builder.Build();

To retrieve a class reference I am using the below code:

var r = container
    .ResolveNamed<IQCatParser>(Path.GetExtension(fileName).ToUpperInvariant());

Now my question is if a unsuppoted file extension comes let’s say .DOC I want to resolve it with a component among one of the registered classes or else with the first registered class.

Is it possible to do this with AutoFac?

Answer 1

You can do this with Autofac. You need to create an IRegistrationSource that can provide the default registration if needed. For example, here is the RegistrationsFor code of a source that provides settings classes:

var typedService = service as IServiceWithType;
if (typedService != null && typedService.ServiceType.IsClass && typeof(ISettings).IsAssignableFrom(typedService.ServiceType))
{
    yield return RegistrationBuilder.ForDelegate((c, p) => c.Resolve<ISettingsReader>().Load(typedService.ServiceType))
                .As(typedService.ServiceType)
                .CreateRegistration();
}

Then, inside of a module or directly using your Autofac builder, call RegisterSource to hook up the new registration source.