Unity, RegisterType<> and Singleton objects

Question

I am using Unity to instantiate some objects and I'm finding that no matter what I try, Unity is creating singletons for my objects.

According to the documentation: http://msdn.microsoft.com/en-us/library/dd203242.aspx#Y500

With the following code I should be getting a different instance every time the interface gets resolved.

IUnityContainer myContainer = new UnityContainer();  

// Register a default (un-named) type mapping with a transient lifetime  
myContainer.RegisterType<IMyObject, MyRealObject>();  
// Following code will return a new instance of MyRealObject  
myContainer.Resolve<IMyObject>();

But instead I'm getting a singleton instance.

Below is my declaration. Global.asax

// This should get me a singleton  
container.RegisterType<IRetailerService, RetailerService>(new ContainerControlledLifetimeManager(), new InjectionConstructor());  
// This is the one giving me trouble.
container.RegisterType<IInStoreRetailersViewModelBuilder, InStoreRetailersViewModelBuilder>(new InjectionConstructor(container.Resolve<IRetailerService>()));  
container.RegisterType<CollectController>(new InjectionConstructor(container.Resolve<IInStoreRetailersViewModelBuilder>()));

Controller

private readonly IInStoreRetailersViewModelBuilder _inStoreRetailersViewModelBuilder;  

public CollectController(IInStoreRetailersViewModelBuilder inStoreRetailersViewModelBuilder)  
{  
    this._inStoreRetailersViewModelBuilder = inStoreRetailersViewModelBuilder;  
}  

public ActionResult Index()  
{  
    InStoreViewModel viewModel = this._inStoreRetailersViewModelBuilder.WithRetailers().WithPostcode().Build();  
}

If I open Chrome and run the Index action, and then I go and open internet explorer and call the Index action, on the second call, in the constructor the inStoreRetailersViewModelBuilder parameter that gets injected is the one generated on the first call (with Chrome).

I've tried using the PerResolveLifetimeManager() and even the PerHttpRequestLifetime() from this thread: MVC, EF - DataContext singleton instance Per-Web-Request in Unity

But nothing seems to give me a brand new instance. Anyone can shed some light on what I may be doing wrong here?

score 9 · Accepted Answer · answered Aug 09 '11 at 16:42

9

Try this and see if it helps.

container.RegisterType<IInStoreRetailersViewModelBuilder, InStoreRetailersViewModelBuilder>(
new InjectionConstructor(
    new ResolvedParameter<IRetailerService>()));  
container.RegisterType<CollectController>(
new InjectionConstructor(
    new ResolvedParameter<IInStoreRetailersViewModelBuilder>()));

Maybe by resolving the parameter to your constructor yourself you are essentially passing in a specific instance which results in it being a singleton.

answered Aug 09 '11 at 16:42

MLF

626
4
15

That works! What's the difference between using Container.Resolve and new ResolvedParameter? I am not an expert on Unity and although for the most part it works great, sometimes it has me scratching my head. Thanks for the help! – Yag Aug 10 '11 at 07:55
3

I THINK the difference is that by using Container.Resolve you are passing in an existing object to the constructor so it will always use that existing object. When you use ResolvedParameter Unity will resolve a new object each time and pass it to the constructor. Have a look at the documentation you linked to, I think the first example in the Using a Lifetime Manager with the RegisterInstance Method section is equivalent to what you were doing. – MLF Aug 10 '11 at 13:15

Unity, RegisterType<> and Singleton objects

1 Answers1