Nested resolution - dependency-injection

Question

Say I have:
ProductA
ProductB
ProductScreen
ProductAScreen1 : ProductScreen
ProductAScreen2 : ProductScreen
ProductBScreen1 : ProductScreen
ProductBScreen2 : ProductScreen
How can I set it up so that I register the screens locally to the product? So when I am in ProductA and passing IEnumerable it doesn't resolve ProductB's screens?
I thought this would be achievable using something like the lifetime scope, but it doesn't appear I understood it correctly.

Answer 1

Lifetime scope is used to control instance lifetime. You are talking about controlling selection. For that, you should look at the metadata features in Autofac.
Using metadata, you can "tag" each product screen, indicating which product it belongs to:
builder.Register(c => new ProductAScreen1()).As<ProductScreen>()
.WithMetadata<IProductScreenMetadata>(m =>
m.For(am => am.ProductType, typeof(ProductA)));
builder.Register(c => new ProductAScreen2()).As<ProductScreen>()
.WithMetadata<IProductScreenMetadata>(m =>
m.For(am => am.ProductType, typeof(ProductA)));
builder.Register(c => new ProductBScreen1()).As<ProductScreen>()
.WithMetadata<IProductScreenMetadata>(m =>
m.For(am => am.ProductType, typeof(ProductB)));
builder.Register(c => new ProductBScreen2()).As<ProductScreen>()
.WithMetadata<IProductScreenMetadata>(m =>
m.For(am => am.ProductType, typeof(ProductB)));
Next, you can take a dependency on a IEnumerable<Lazy<ProductScreen, IProductScreenMetadata>> and resolve screens according to product type:
var productScreens = _screens.WHere(a => a.Metadata.ProductType == typeof(ProductA));
Update: for completeness, here is a simpler solution using the Keyed approach. First, registration is much simpler:
builder.RegisterType<ProductAScreen1>().Keyed<ProductScreen>(typeof(ProductA));
builder.RegisterType<ProductAScreen2>().Keyed<ProductScreen>(typeof(ProductA));
builder.RegisterType<ProductBScreen1>().Keyed<ProductScreen>(typeof(ProductB));
builder.RegisterType<ProductBScreen2>().Keyed<ProductScreen>(typeof(ProductB));
To resolve a collection of keyed services we'll have to take a dependency on the IIndex<,> type:
public class SomeService
{
private IEnumerable<ProductScreen>> _screens;
public SomeService(IIndex<Type, IEnumerable<ProductScreen>> screens)
{
_screens = screens;
}
public void DoSomething()
{
var screensForProductA = _screens[typeof(ProductA)];
}
}
Note: for the curious: instead of hardcoding the type registrations, here's how you can do a "by convention" registration:
var assembly = ...;
var productTypes = ...; // a collection of all the product types
foreach(var productType in productTypes)
{
builder.RegisterAssemblyTypes(assembly)
.Where(t => typeof(ProductScreen).IsAssignableFrom(t))
.Where(t => t.Name.StartsWith(productType.Name))
.Keyed<ProductScreen>(productType);
}