I'm trying to inject a dependency to my MVC controllers like this

private static void RegisterContainer(IUnityContainer container)
{            
    container
        .RegisterType<IUserService, UserService>()
        .RegisterType<IFacebookService, FacebookService>();
}

The UserService class has a constructor like this...

public UserService(): this(new UserRepository(), new FacebookService())
{
    //this a parameterless constructor... why doesnt it get picked up by unity?
}

public UserService(IUserRepository repository, IFacebookService facebook_service)
{
    Repository=repository;
    this.FacebookService=facebook_service;
}

The exception I am getting is the following...

The current type, Repositories.IUserRepository, is an interface and cannot be constructed. Are you missing a type mapping?

It looks like it's trying to inject a constructor into the service, but the default would suffice? Why is it not mapping to the parameterless constructor?

c# asp.net-mvc unity-container ioc-container
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