Question

I have an interface, IFoo, and three concrete classes: FooA : IFoo, FooB : IFoo, and MultiFoo : IFoo.

The constructor for MultiFoo looks like this:

public MultiFoo(params IFoo[] foos) { ... }

Can I specify particular resolution overrides when registering MultiFoo in Unity? I would like to be able to do something like this:

container.RegisterType<IFoo, FooA>("Foo A");
container.RegisterType<IFoo, FooB>("Foo B");

container.RegisterType<IFoo, MultiFoo>(new ContainerControlledLifetime(),
    new ResolvedOverride<IFoo>("Foo A"),
    new ResolvedOverride<IFoo>("Foo B")
);

which would then pass a resolved FooA and a resolved FooB to the constructor at resolve-time:

new MultiFoo(new FooA(), new FooB())

Answer 1

params are compiler syntactic sugaring, you’re really passing an array as a single parameter. To match that you’d configure the container like this:

container.RegisterType<IFoo, MultiFoo>(new ContainerControlledLifetimeManager(),
    new InjectionConstructor(new ResolvedArrayParameter<IFoo>(new ResolvedParameter<IFoo>("Foo A"), new ResolvedParameter<IFoo>("Foo B"))));

Resolver overrides are used at Resolve time, not at container setup time. The equivalent using resolve overrides would look like this:

container.RegisterType<IFoo, MultiFoo>(new ContainerControlledLifetimeManager());

var foo = container.Resolve<IFoo>(
    new ParameterOverride(
        "foos", 
        new ResolvedArrayParameter<IFoo>(new ResolvedParameter<IFoo>("Foo A"), new ResolvedParameter<IFoo>("Foo B"))));