CODEWITHSUNDEEP
c#castle-windsor
Neil Menzies
Neil Menzies

Reputation: 91

Castle Windsor resolve zero or more implementations

(Slightly simplified scenario to highlight the specific issue).

I'm trying to use Castle Windsor to resolve a component, which has a constructor with a single parameter which is an array of a service interface:

public class TestClass<T>
{
    public TestClass(IService<T>[] services)
    {
        ...
    }
}

The Windsor container is configured to use the ArrayResolver:

container.Kernel.Resolver.AddSubResolver(new ArrayResolver(container.Kernel));

This all works fine, and one or more services are injected for various instances of T.

However, for some T, there are no implementations of IService<T>. The goal would be for the constructor to be called with a zero-length array.

The issue is, if there are no concrete implementations of IService for a given T, how do I register the definition of IService with no implementation, so the container is aware of the type?

I'm current using:

container.Register(
    Classes.FromAssembly(Assembly.GetExecutingAssembly())
        .BasedOn<IService<>>()
        .WithService.FirstInterface());

but since this is driven from the concrete classes, it's obviously not registering any 'unused' IService.

Fallback is to provide a stub implementation of IService for any T which doesn't have a 'real' implementation, but I'd prefer not to pollute the code with many such stubs. (Could also provide through an open generic with some reflection...).

Upvotes: 5

Views: 522

Answers (1)

Neil Menzies
Neil Menzies

Reputation: 91

Answering my own question, having been directed to it by a colleague...

Registering the ArrayResolver with a second parameter specifies allowing empty arrays - which is the case if the component in question is not registered:

container.Kernel.Resolver.AddSubResolver(new ArrayResolver(container.Kernel, true));

so the behaviour is exactly as desired.

Upvotes: 4

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