How to register a singleton in a child container? - structuremap

Question

I am having trouble registering a singleton in a StructureMap child container.
The singleton has a dependecy which is registered in the same container.
When trying to resolve the singleton, it fails saying it cannot determine the dependency. Whereas I can resolve the depency manually without problem.
The following code snippet shows the issue:
[Test]
public void should_be_able_to_instantiate_root()
{
var parentContainer = new Container();
var childContainer = parentContainer.CreateChildContainer();
childContainer.Configure(x =>
{
x.ForSingletonOf<IRoot>().Use<Root>();
x.For<IDependency>().Use<Dependency>();
});
Console.WriteLine(childContainer.WhatDoIHave());
var dependency = childContainer.GetInstance<IDependency>(); // Works
var root = childContainer.GetInstance<IRoot>(); // Fails ("No default Instance is registered and cannot be automatically determined for type 'IDependency'")
}
public interface IRoot
{
}
public class Root : IRoot
{
public Root(IDependency dependency)
{
}
}
public interface IDependency
{
}
public class Dependency : IDependency
{
}
childContainer.GetInstance<IRoot>() throws the following exception:
StructureMap.StructureMapConfigurationException : No default Instance is registered and cannot be automatically determined for type 'StructureMapIssue.IDependency'
There is no configuration specified for StructureMapIssue.IDependency
1.) new Root(*Default of IDependency*)
2.) StructureMapIssue.Root
3.) Instance of StructureMapIssue.IRoot (StructureMapIssue.Root)
4.) Container.GetInstance(StructureMapIssue.IRoot)
Here is the output from childContainer.WhatDoIHave(), you can see IDependency is there:
Profile is 'DEFAULT'
========================================================================================================
PluginType Namespace Lifecycle Description Name
--------------------------------------------------------------------------------------------------------
Func<TResult> System Transient Open Generic Template for Func<> (Default)
--------------------------------------------------------------------------------------------------------
Func<T, TResult> System Transient Open Generic Template for Func<,> (Default)
--------------------------------------------------------------------------------------------------------
IContainer StructureMap Transient Object: StructureMap.Container (Default)
--------------------------------------------------------------------------------------------------------
IDependency StructureMapIssue Transient StructureMapIssue.Dependency (Default)
--------------------------------------------------------------------------------------------------------
IRoot StructureMapIssue Singleton StructureMapIssue.Root (Default)
--------------------------------------------------------------------------------------------------------
Lazy<T> System Transient Open Generic Template for Func<> (Default)
--------------------------------------------------------------------------------------------------------
Root StructureMapIssue Transient StructureMapIssue.Root (Default)
========================================================================================================
Am I doing something wrong?

Answer 1

It doesn't male much sense to register a singleton in a child container, considering that the default behaviour of something being instantiated in a child container is that the instance sticks around until the child container is disposed.
Additionally, a child container is not meant to stick around for a long time - at least not as long as the parent.