When do you need SimpleInjector hybrid registration? (How can an IIS hosted object be called without the HttpContext?)

Following on from my recent question regarding SimpleInjector and hybrid web request / lifestyle in thread , it seems I do not fully understand the technical requirements and do what I do, t really need to be done.

With this code

interface IUnitOfWork { }
interface IWebUnitOfWork : IUnitOfWork { }
interface IThreadUnitOfWork : IUnitOfWork { }
class UnitOfWork : IWebUnitOfWork, IThreadUnitOfWork { }

container.RegisterPerWebRequest<IWebUnitOfWork, UnitOfWork>();
container.RegisterLifetimeScope<IThreadUnitOfWork, UnitOfWork>();
container.Register<IUnitOfWork>(() => container.GetInstance<UnitOfWork>());

// Register as hybrid PerWebRequest / PerLifetimeScope.
container.Register<UnitOfWork>(() =>
{
    if (HttpContext.Current != null)
        return container.GetInstance<IWebUnitOfWork>() as UnitOfWork;
    else
        return container.GetInstance<IThreadUnitOfWork>() as UnitOfWork;
});

      

        
        
        
      

    

I figured out that for AppDomains running in IIS, there would IWebUnitOfWork

be an error returned , and otherwise there would be an error unless I explicitly declared the LifetimeScope instance to carry the call to the container (which would return IThreadUnitOfWork

).

The following expression made me realize that I didn't quite understand what I was doing!

However, you don't seem to need a hybrid lifestyle. A hybrid lifestyle is a lifestyle that can switch dynamically (on every GetInstance call and every injection) while you feel like you need to switch during startup.

My question is this: under what circumstances does a container (or any other class for that matter), whether static or an instance loaded inside an AppDomain running in IIS, get called without the existence of the HttpContext?