Autofac: Check if instance is already resolved

Question

I do this: https://stackoverflow.com/questions/12069002/autofac-resolve-with-and-without-named-parameter

I register an interface. For the initialization a parameter is needed. A first call will pass this parameter.

On another place i want to resolve this instance of the interface too, but i don't can pass this parameter. Is it possible to check if this interface was already resolved (in the current scope. I use the ASP.NET WEB API)? If i resolve it without the parameter, I get an exception.

I need to check if in the current HttpRequest-scope the is already resolved (so I can get it without passing the parameter, because if it is already resolved, the registered creation-delegate will not be called twice)

m_builder.Register<IMyClass((c, p) =>
    {
        //...
        return new MyClass;

    }).InstancePerHttpRequest();//.InstancePerApiRequest();

Answer 1

First, create a class that can track whether the instance is resolved or not:

public class Tracker
{
    public bool IsResolved { get; set; }
}

(You may wish to pretty this up a bit :))

Register it with the same scope as whatever you want to track:

builder.RegisterType<Tracker>()
    .InstancePerHttpRequest();

Then, in the OnActivated event, set the bool:

builder.Register((c, p) => {
        return new MyClass();
    })
    .As<IMyClass>()
    .InstancePerHttpRequest()
    .OnActivated(e => {
        e.Context.Resolve<Tracker>().IsResolved = true;
    });

You could also set the field during activation (in the first delegate) but using the OnActivated event makes it easier to generalise this if you want to.

Finally, to check the field:

if (container.Resolve<Tracker>().IsResolved) { ... }