Unity Register two interfaces as one singleton

Question

Hi all, how do I register two different interfaces in Unity with the same instance... Currently I am using

        _container.RegisterType<EventService, EventService>(new ContainerControlledLifetimeManager());
        _container.RegisterInstance<IEventService>(_container.Resolve<EventService>());
        _container.RegisterInstance<IEventServiceInformation>(_container.Resolve<EventService>());

which works, but does not look nice..

So, I think you get the idea. EventService implements two interfaces, I want a reference to the same object if I resolve the interfaces.

Chris

Answer 1

Edit

After some feedback in the comments I've decided that Sven's answer is a much superior answer. Thanks to Chris Tavares for pointing out the technical merits.

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That's pretty much the only way to do it.

You could modify it slightly (I hate RegisterType with the same type for each generic parameter):

EventService es = _container.Resolve<EventService>();
_container.RegisterInstance<IEventService>(es);
_container.RegisterInstance<IEventServiceInformation>(es);

If one or more of your IoC children is going to request the concrete EventService type (hopefully not) you'd add one more RegisterInstance of type RegisterInstance<EventService>. Hopefully you don't need that and all of the dependent objects are asking for an IEventService, rather than an EventService.

Hope this helps, Anderson

Answer 2

I had the same issue, and decided the best solution was a slight design change. Could you not merge interfaces, and resolve by that?

interface IEventServiceHolder : IEventService, IEventServiceInformation
{
}

class EventService : IEventServiceHolder
{
   .. yadda yadda .. 
}

Then simply register it once:

container.RegisterType<IEventServiceHolder>();

and resolve

var k = container.Resolve<IEventServiceHolder>();

Answer 3

A little late an answer, but should do the trick:

_container.RegisterType<EventService>(new ContainerControlledLifetimeManager());
_container.RegisterType<IEventService, EventService>();
_container.RegisterType<IEventServiceInformation, EventService>();

bool singleton = ReferenceEquals(_container.Resolve<IEventService>(), _container.Resolve<IEventServiceInformation>());