How to remove(unregister) registered instance from Unity mapping?

Question

I meet one problem that i can't solve now. I have the following:

UnityHelper.DefaultContainer.RegisterInstance(typeof(IMyInterface), "test", instance);

where UnityHelper.DefaultContainer is my helper for getting unity container with loaded configuration.

here I registered instance as an instance of IMyInterface.

So anywhere( some time after using) I want to remove this mapping. Remove it at all. How I can do it?

I have tried:

UnityHelper.DefaultContainer.Teardown(instance)

but is was unsuccessful and the following code returns instance anyway:

UnityHelper.DefaultContainer.ResolveAll<IMyInterface>()

Answer 1

I had the same problem and just removed the registrations of the ContainerControlledLifetimeManager from my Container:

foreach (var registration in container.Registrations
    .Where(p => p.RegisteredType == typeof(object)
                && p.Name == name
                && p.LifetimeManager.Type == typeof(ContainerControlledLifetimeManager)))
{
    registration.LifetimeManager.RemoveValue();
}

Answer 2

I think that is what you are looking for.

var lifetimeManager = new TransientLifetimeManager();
UnityHelper.DefaultContainer.RegisterInstance(typeof(IMyInterface), "test", instance, lifetimeManager);
lifetimeManager.RemoveValue();

Answer 3

This is an old question, but some answers are misleading, so I will provide my own. You can´t do that with Unity. End of the story. Calling RemoveValue on registrations lifetime managers does not achieve unregistration (more information about lifetime managers), and that method is not intended to unregister anything. So the final behaviour is unexpected and not convenient. Of course, RemoveValue makes even less sense if you register an implementation or a factory method, although the question is about unregistering instances. Consider the next piece of code

    public interface SomeInterface
    {
        int Foo { get; set; }
    }

    public class SomeImplementation: SomeInterface
    {
        public int Foo { get; set; }
    }

    static void Main(string[] args)
    {
        UnityContainer iocContainer = new UnityContainer();
        string registerName = "instance";
        //before any registration
        Resolve<SomeInterface>(iocContainer, registerName);

        iocContainer.RegisterInstance<SomeInterface>(registerName, new SomeImplementation());

        //after registration
        Resolve<SomeInterface>(iocContainer, registerName);

        ClearValue<SomeInterface>(iocContainer, registerName);

        //after clear value
        Resolve<SomeInterface>(iocContainer, registerName);


    }

    private static void Resolve<T>(UnityContainer iocContainer,string name)
    {
        if (iocContainer.IsRegistered<T>(name))
            iocContainer.Resolve<T>(name);

        iocContainer.ResolveAll<T>();
    }
    private static void ClearValue<T>(UnityContainer iocContainer, string name)
    {
        foreach (var registration in iocContainer.Registrations.Where(p => p.RegisteredType == typeof(T)
            && p.Name==name))
        {
            registration.LifetimeManager.RemoveValue();
        }
    }

If you debug it, you will see that after the call to ClearValue, the container still says it is registered, but if you try to resolve that instance it will throw an exception. What is even worse, calls to ResolveAll<T> will fail too.

To Sum up, no matter if you do ClearValue, wrap around your register instance with another IoC or a custom class, or provide your own LifeTimeManager, ResolveAll<T> and IsRegistered<T> won´t behave as expected, and the registration will still be there. So don't try it because it won´t work and it will cause problems down the road.

Answer 4

Here is how I handled unregistering instances from a unity container

I needed to implement Add/Remove functionality like this:

public interface IObjectBuilder
{
    void AddInstance<T>(T instance);
    void RemoveInstance<T>(T instance);
}

I created a custom lifetime manager to do the implementation

public class ExplicitLifetimeManager :
    LifetimeManager
{
    object Value;

    public override object GetValue()
    {
        return Value;
    }

    public override void SetValue(object newValue)
    {
        Value = newValue;
    }

    public override void RemoveValue()
    {
        Value = null;
    }
}

Here is the final implementation:

    Dictionary<object, ExplicitLifetimeManager> Instances = new Dictionary<object, ExplicitLifetimeManager>();

    public void AddInstance<T>(T instance)
    {
        ExplicitLifetimeManager e = new ExplicitLifetimeManager();
        Instances[instance] = e;
        Container.RegisterInstance(instance, e);
    }

    public void RemoveInstance<T>(T instance)
    {
        Instances[instance].RemoveValue();
        Instances.Remove(instance);
    }

calling removevalue on the custom lifetime manager causes the instance to be unregistered

Answer 5

I have the same challenge and after experimenting I solved it by using the standard ContainerControlledLifetimeManager and calling RemoveValue when I want to remove the container instance. Note that if you are not using interfaces and your object has constructor which the container can find and use it will recreate the instance after you have destroyed it with lifetimeManager.RemoveValue().

[TestClass]
public class UnityContainerTest
{
    [TestMethod]
    public void RemoveFromContainer()
    {
        UnityContainer container = new UnityContainer();
        MyUnityMember member = new MyUnityMember(5);

        LifetimeManager lifetimeManager = new ContainerControlledLifetimeManager();
        container.RegisterInstance(member, lifetimeManager);

        var resolved = container.Resolve<MyUnityMember>();
        Assert.IsNotNull(resolved);

        lifetimeManager.RemoveValue();

        try
        {
            resolved = container.Resolve<MyUnityMember>();
            Assert.Fail(resolved + " is still in the container");
        }
        catch (ResolutionFailedException)
        {
        }
    }

    public class MyUnityMember
    {
        public MyUnityMember(int x)
        {
            I = x;
        }

        public int I { get; private set; }
    }
}

Answer 6

I had a similar requirement whereby I wanted to temporarily store objects in the unity container and found this was not possible (or at least easily possible). If your objective is to have a temporary storage place easily available to unity, then create a temporary storage service.

public class TemporaryStorageService : ITemporaryStorageService
{
    public void Deposit<T>(Object o, string key)
    {
        System.Windows.Application.Current.Properties[key] = o;
    }

    public T Withdraw<T>(string key)
    {   T o = (T)System.Windows.Application.Current.Properties[key];
        System.Windows.Application.Current.Properties.Remove(key);
        return o;
    }
}

Register your service with Unity. Then when you wish to store an object you call the Deposit Method and when you wish to remove the object you call the Withdraw method. A fuller explanation can be found here