Simone,

        container.RegisterType<UmbracoContext>(
                new ContainerControlledLifetimeManager(),
                new InjectionFactory(c => UmbracoContext.Current));

UmbracoContext.Current will be used to create the Singleton object and as it is singleton it will be created only once... the injected value will be the UmbracoContext.Current of your first request.

The only good reason I think it doesn't break the MVC Unity configuration, is that UmbracoContext.Current reference is not widely used through constructors , or if it used maybe it is used for some global properties that are the same through all requests.

Did you manage to resolve your issues with this? Everything appears to be working ok for me except when I try to create a new content item via a list view at which point I get the same exception as you. I am using Unity.Mvc5 and Unity.AspNet.WebApi and in the WebActivator class I have the following in the Start() method:

// Web API
GlobalConfiguration.Configuration.DependencyResolver = new UnityDependencyResolver(UnityConfig.Container); ; ;
// MVC
DependencyResolver.SetResolver(new Unity.Mvc5.UnityDependencyResolver(UnityConfig.Container));

UnityConfig.RegisterComponents();

And in my UnityConfig class I have the following:

public static class UnityConfig

    private static Lazy<IUnityContainer> container =
        new Lazy<IUnityContainer>(() =>
            {
                var container = new UnityContainer();
                return container;
            });

    public static IUnityContainer Container => container.Value;

    public static void RegisterComponents()
    {
        // Register our type mappings
        RegisterTypes(Container);
    }

    public static void RegisterTypes(IUnityContainer container)
    {
        container.RegisterType<UmbracoContext>(new ContainerControlledLifetimeManager(), new InjectionFactory(c => UmbracoContext.Current));
        container.RegisterType<ApplicationContext>(new ContainerControlledLifetimeManager(), new InjectionFactory(c => UmbracoContext.Current));
        container.RegisterType<ServiceContext>(new ContainerControlledLifetimeManager(), new InjectionFactory(c => UmbracoContext.Current));
        container.RegisterType<Umbraco.Web.Mvc.RenderMvcController>(new InjectionConstructor(new ResolvedParameter<UmbracoContext>()));
        container.RegisterType<UmbracoHelper>(new InjectionConstructor(new ResolvedParameter<UmbracoContext>()));
        container.RegisterType<LegacyTreeController>(new InjectionConstructor());
        container.RegisterType<HealthCheckController>(new InjectionConstructor());
        container.RegisterType<UsersController>(new InjectionConstructor());
    }
}

Like Laurent said, UmbracoContext should be created on a per-request basis, not a lifetime basis. The Umbraco context contains info on the current request, which changes per request. It's equivalent to HttpContext in that regard.

See https://our.umbraco.org/Documentation/Reference/Common-Pitfalls/

PerThreadLifetimeManager also seems to work and sounds like it might be more suitable:

PerThreadLifetimeManager. For this lifetime manager Unity returns, on a per-thread basis, the same instance of the registered type or object each time you call the Resolve or ResolveAll method or when the dependency mechanism injects instances into other classes. This lifetime manager effectively implements a singleton behavior for objects on a per-thread basis. PerThreadLifetimeManager returns different objects from the container for each thread. If you registered a type mapping using configuration or using the RegisterType method, Unity creates a new instance of the registered type the first time the type is resolved in a specified thread, either to answer a call to the Resolve or ResolveAll method for the registered type or to fulfill a dependency while resolving a different type. Subsequent resolutions on the same thread return the same instance.

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