Question

I’m using UnityContainer, and I want to register an interface not with a type, but with another interface.
Unfortunately, I’m unable to do it cleanly..

I have several common interfaces, which are united in one interface, and I need to register them in the container. The code is like the following:

interface IDeviceImporter {
    void ImportFromDevice();
}

interface IFileImporter {
    void ImportFromFile();
}

interface IImporter : IDeviceImporter, IFileImporter {
}


class Importer1: IImporter {
}
class Importer2: IImporter {
}

When entering the library, I know which importer to use, so the code is like:

var container = new UnityContainer();
if (useFirstImport) {
    container.RegisterType<IImporter, Importer1>();
} else {
    container.RegisterType<IImporter, Importer2>();
}

and then I want to register this specific class with IDeviceImporter and IFileImporter also. I need something like:

container.RegisterType<IDeviceImporter, IImporter>();

But with that code I’m getting an error: IImporter is an interface and cannot be constructed.

I can do it inside the condition, but then it’ll be copy-paste. I can do

container.RegisterInstance<IDeviceImporter>(container.Resolve<IImporter>());

but it’s really dirty.
Anyone please, advice me something 🙂

Answer 1

I’m using ContainerControlledLifetimeManager, and end up with a code like:

var container = new UnityContainer();
System.Type importerType
if (useFirstImport) {
    importerType = GetType(Importer1);
} else {
    importerType = GetType(Importer2);
}

container.RegisterType(GetType(IImporter), importerType);
container.RegisterType(GetType(IDeviceImporter), importerType);
container.RegisterType(GetType(IFileImporter), importerType);

But yes, the best thing would be to have something like:

container.CreateSymLink<IDeviceImporter, IImporter>()