Retrieve instantiated types from UnityContainer

Question

(Using Unity 4.0.1)

Given a UnityContainer object, is there any way to retrieve all the objects that have been instantiated by the container up to that point in time? E.g. something like

IEnumerable<object> instantiatedObjects = unityContainer.GetAllInstantiatedObjects();

or, even better, filtering according to those that derive from a given type:

IEnumerable<IFoo> instantiatedFoos = unityContainer.GetAllInstantiatedObjects<IFoo>();

Answer 1

Following RB's suggestion, the following approach implements a custom Unity extension with a strategy that keeps a reference to each instantiated object upon PostInitializtion.

N.B. The following code is for illustration only, and is not intended to be thread-safe/exception-safe etc.

First, the implementation of the Extension class and other classes it relies on.

public class ObjectContainer
{
    private readonly List<object> _instantiatedObjects = new List<object>();
    public void Add(object instantiatedObject)
    {
        _instantiatedObjects.Add(instantiatedObject);
    }
    public IEnumerable<object> GetInstantiatedObjects()
    {
        return _instantiatedObjects;
    }
    public IEnumerable<T> GetInstantiatedObjects<T>()
    {
        return GetInstantiatedObjects().OfType<T>();
    }
}

public class InstantiatedObjectsStrategy : BuilderStrategy
{
    private readonly ObjectContainer _objectContainer;
    public InstantiatedObjectsStrategy(ObjectContainer objectContainer)
    {
        _objectContainer = objectContainer;
    }
    public override void PostBuildUp(IBuilderContext context)
    {
        _objectContainer.Add(context.Existing);
    }
}

public class InstantiatedObjectsExtension : UnityContainerExtension
{
    private readonly ObjectContainer _objectContainer = new ObjectContainer();
    protected override void Initialize()
    {
        Context.Container.RegisterInstance(_objectContainer);
        Context.Strategies.Add(new InstantiatedObjectsStrategy(_objectContainer),
            UnityBuildStage.PostInitialization);
    }
}

The extension can be added to the UnityContainer immediately after creation:

IUnityContainer container = new UnityContainer();
container.AddNewExtension<InstantiatedObjectsExtension>();

The instantiated objects can then be retrieved from the container at a later stage as follows:

IEnumerable<object> instantiatedObjects = container.Resolve<ObjectContainer>().GetInstantiatedObjects();
IEnumerable<Foo> instantiatedFoos = container.Resolve<ObjectContainer>().GetInstantiatedObjects<Foo>();