Configure Unity for Inherted Interfaces

Question

I am fairly new to Unity, (well, IoC and DI in general), and am having problems configuring it for my use.

I have two interfaces:

public interface ISample { ... }

and

public interface IDerivedSample : ISample { ... }

and a number of concreate classes simular to:

public class UseSample : IDerivedSample { ... }

I am attempting to configure Unity to resolve these when used like this:

public class UsesSample
{
    private ISample _sample;

    public UsesSample(ISample sample) 
    {
        _sample = sample;
    }
}

My attempts at getting this configured is failing, so I thought I would ask the crowd on how to do so.

EDIT

I have already configured the container to find the different versions of the interfaces by name, so the resulting code for resolving UserSample should be simular to:

ISample = contianer.Resolve<ISample>("derived");

However, it is failing.

Answer 1

The short answer

container.RegisterType<ISample, UseSample>();

The longer answer

The code above works if you only register one mapping from ISample to a concrete class. As I read your question, you have many implementations of ISample, in which case ambiquity arises because the UsesSample provides no hint at how to pick a proper ISample instance.

There are several ways out of such a conundrum. Some are specific to the DI Container (in this case Unity) while others solve the issue by creating a less ambiguous API design.

You may, for example, use an Abstract Factory to select a dependency based on a run-time value.