Registration of implementation for IEnumerables only using type parameters

I'm trying to figure out the syntax to register a particular implementation of an interface and I just can't suss it out (using Simple Injector). My interface signature looks like this:

public interface IAdditionalDataService<TResult, TModel>

I would like to register an implementation for whenever the first type parameter is an IEnumerable of type TModel, for example:

public class CompositeAdditionalDataService<TModel>
                 : IAdditionalDataService<IEnumerable<TModel>, TModel>

How would I do this?

I've tried this:

container.RegisterOpenGeneric(typeof(IAdditionalDataService<,>),
    typeof(CompositeAdditionalDataService<>));

And I get an error when I verify the container saying that there is no registration for IAdditionalDataService<List<User>, User>, so my registration has not worked.

I've also tried this:

container.RegisterOpenGeneric(typeof(IAdditionalDataService<IEnumerable<>,>),
    typeof(CompositeAdditionalDataService<>));

But this doesn't even compile, obviously, because it's not valid syntax.

So my question is

How can I register my implementation so it is used whenever a IAdditionalDataService, TModel> is requested, where TModel is a type parameter, so it could be almost anything?

Solution

You should change your generic implementation to the following:

public class CompositeAdditionalDataService<TCollectionResult, TModel>
    : IAdditionalDataService<TCollectionResult, TModel>
    where TCollectionResult : IEnumerable<TModel>

and register it as follows:

// Simple Injector v3.x
container.Register(
    typeof(IAdditionalDataService<,>),
    typeof(CompositeAdditionalDataService<,>));

// Simple Injector v2.x
container.RegisterOpenGeneric(
    typeof(IAdditionalDataService<,>),
    typeof(CompositeAdditionalDataService<,>));