Child kernel bindings not being used to resolve dependencies

[pedroreys]

I'm creating a child kernel and overriding the binding of a specific interface. My expectation is that all dependency resolutions using the child kernel will use this new binding. But, that's not what I'm seeing. The parent kernel binding is being used instead.

Here is a test that reproduces the issue:

public interface IA
{
    string GetValue();
}

public class A : IA
{
    private IB _b;

    public A(IB b)
    {
        _b = b;
    }

    public string GetValue()
    {
        return _b.Value;
    }
}

public interface IB
{
    string Value { get; set; }
}
public class B : IB
{
    public string Value { get; set; }
}


 public class TestRepro
  {
   [TestMethod]
    public void Should_not_use_Parents_Bindings()
    {
        var parentKernel = new StandardKernel();

        parentKernel.Bind<IA>().To<A>();
        parentKernel.Bind<IB>().To<B>();

        var childKernel = new ChildKernel(parentKernel);

        var otherB = new B() { Value = "newValue" };

        childKernel.Bind<IB>().ToConstant(otherB);

        childKernel.Get<IB>().Value.ShouldEqual(otherB.Value);

        childKernel.Get<IA>().GetValue().ShouldEqual(otherB.Value);

        // This last assertion fails. The value returned by IA.GetValue() is null
    }
}

[remogloor]

An object resolved on the parent kernel will never use any bindings from the child kernel. Just think what would happen in the following scenario:

    parentKernel.Bind<IA>().To<A>()InSingletonScope();
    parentKernel.Bind<IB>().To<B>();

    var a1 = parent.Get<IA>(); // note it doesn't know about a childkernel yet

    var childKernel = new ChildKernel(parentKernel);
    var otherB = new B() { Value = "newValue" };
    childKernel.Bind<IB>().ToConstant(otherB);

    var a2 = childKernel.Get<IA>();

    a1.SholdBeSameAs(a2);

    // but you want also:
    a2.GetValue().ShouldEqual(otherB.Value);

Only one of those expectances can be fulfilled. Therefore the decission: An object resolved from a kernel will never get any dependency from child kernels. Just the other way is supported. objects resolved on child kernel can get objects from the parent kernel.

You probably want to use NamedScopes with one kernel to solve your problem.