Skip to main content

Collections

When a service has several implementations, ask for a collection to get them all. Every syrup on the bar is an ISyrup. A consumer that wants the whole set asks for a collection of them.

Resolve every implementation​

Register the implementations, then depend on a collection shape.

[Container]
[Singleton<VanillaSyrup, ISyrup>]
[Singleton<CaramelSyrup, ISyrup>]
[Singleton<HazelnutSyrup, ISyrup>]
public static partial class CoffeeShop;

public sealed class SyrupBar(IEnumerable<ISyrup> syrups);

Supported shapes​

Any of these constructor parameter types works, and each is resolvable by type as well.

IEnumerable<ISyrup>
ISyrup[]
IReadOnlyList<ISyrup>
IReadOnlyCollection<ISyrup>
IList<ISyrup>
ICollection<ISyrup>

Members come back in registration order. Each keeps its own lifetime. A service type with no registrations resolves to an empty collection, not an error.

Async collections​

If a member is async-initialized, you have two shapes.

IAsyncEnumerable<T> streams the members and awaits each one's initialization as you go.

public sealed class Warmer(IAsyncEnumerable<IDrink> drinks);

An awaited collection like Task<IReadOnlyList<T>> materializes and awaits every async member, but launders the taint so a synchronous consumer can still hold it.

Task<IReadOnlyList<IDrink>> drinks = shop.Resolve<Task<IReadOnlyList<IDrink>>>();

Registering your own collection​

Register a collection shape explicitly and it wins. Awaiten stops synthesizing the collection for that element type and uses yours.

[Singleton<SyrupBundle, IEnumerable<ISyrup>>]

Where to go next​