Factory method only called once - unity-container

Question

Following is my register code
container.RegisterType<IFoo, Foo>(
new InjectionConstructor(typeof (IEnumerable<int>),
new ResolvedParameter<IBar1>,
new InjectionParameter<IBar2>(CreateBar2(container)))
Problem is CreateBar2(container) is only called once when program startup, I need it called everytime IFoo resolved
Another question, which one is best practice
container.RegisterType<IFoo, Foo>(
new InjectionConstructor(typeof (IEnumerable<int>),
new ResolvedParameter<IBar1>,
new InjectionParameter<IBar2>(CreateBar2(container)))
or
container.RegisterType<IFoo, Foo>(
new InjectionConstructor(typeof (IEnumerable<int>),
new ResolvedParameter<IBar1>,
CreateBar2(container))

Answer 1

First, you need to use a different LifetimeManager. TransientLifetimeManager will resolve a new instance every time.
container.RegisterType<IFoo, Foo>(
new InjectionConstructor(typeof (IEnumerable<int>),
new ResolvedParameter<IBar1>,
new InjectionParameter<IBar2>(CreateBar2(container)),
new TransientLifetimeManager())
This means that every time IFoo is injected or resolved it will call the constructor each time. However, it seems as you're injecting a method, which will be executed at registration - CreateBar2(container). It's the same thing as writing:
var bar2 = CreateBar2(container); // Called once.
container.RegisterType<IFoo, Foo>(
new InjectionConstructor(typeof (IEnumerable<int>),
new ResolvedParameter<IBar1>,
new InjectionParameter<IBar2>(bar2))
I recomend you to abstract this to a class instead and injecting it. This way you can control the calls to that as well.
public interface ICreateBar2
{
IBar CreateBar2();
}
public class CreateBar2
{
private IUnityContainer _container;
public CreateBar(IUnityContainer container)
{
_container = container;
}
public IBar CreateBar2()
{
// Do stuff.
return CreateBar2(_container); // Or what you need to do?
}
}
And change your registration to
container.RegisterType<IFoo, Foo>(
new InjectionConstructor(typeof (IEnumerable<int>),
new ResolvedParameter<IBar1>,
new ResolvedParameter<ICreateBar2>),
new TransientLifetimeManager())
container.RegisterType<ICreateBar2, CreateBar2>(new TransientLifetimeManager());
Or possibly RegisterInstance, if it better suits your needs?
Remember to change the constructor of IFoo to accept ICreateBar instead. The best thing with this approach is that you don't need the InjectionConstructor anymore, since all parameters can be resolved by Unity.
container.RegisterType<IFoo, Foo>(new TransientLifetimeManager());
If your REALLY need to keep the CreateBar2()-method in the current scope, you can inject a Func which actually returns the same value as CreateBar2().
I do not know the complete signature of CreateBar(), but you can do something like this:
container.RegisterType<IFoo, Foo>(
new InjectionConstructor(typeof (IEnumerable<int>),
new ResolvedParameter<IBar1>,
new InjectionParameter<Func<IBar2>>(
new Func<IBar2>(()=> CreateBar2(container)));
But now you need to inject Func<IBar2> to the IFoo constructor. This will cause it to execute whenever you use it in the constructor.
public class Foo : IFoo
{
IBar1 _bar1;
IBar2 _bar2;
public Bar(IBar1 bar1, Func<IBar2> bar2Func)
{
_bar1 = bar1;
_bar2 = bar2Func();
}
}