No way to get scopes tags list for MatchingScopeLifetime

[AqlaSolutions]

I want to be able to get scopes tags from InstancePerMatchingLifetimeScope when iterating through ComponentRegistry.Registrations. E.g. I want to activate everything registered for Application scope but I can't access scopes for components.

Please add this.

[tillig]

Will have to think about this one. Keep in mind there are things like registration sources that dynamically generate registrations. I worry about solutions or features that rely on iterating through the registrations collection.

On the other hand, I could potentially see something where you may query about information for a specific registration. Hmmm.

[tillig]

The initial stated desire here seems to overlap with #731 and #567.

[tillig]

Reading over these now that we've come up for air a bit from the .NET Core RTM, I think if we can address #567 - the ability for AutoActivate/IStartable to work in nested lifetime scopes - that may be the best we can do. We don't actually figure out what the InstancePerMatchingLifetimeScope tags are for things until the component resolves, and even then it's only used to determine which scope owns the component.

Saying something like, "auto-activate everything that was registered just for this matching scope at the time the scope is created" is sort of edge case from an IoC perspective.

One thing you could do to work around the issue is to use events and metadata.

First, when registering things, add metadata to the things you want to auto-activate.

builder.RegisterType<MyComponent>()
  .As<IService>()
  .InstancePerMatchingLifetimeScope("child")
  .WithMetadata("scope", "child");

Then attach to the container ChildLifetimeScopeBeginning event and resolve/activate the things you are interested in:

private static void Activate(IEnumerable<Meta<Lazy<IService>>> services)
{
  foreach(var meta in services)
  {
    if(meta["scope"].Equals("child"))
    {
      // The value of Meta<Lazy<T>> is Lazy<T>
      // The value of Lazy<T> is the resolved instance
      meta.Value.Value.DoActivate();
    }
  }
}

var container = builder.Build();

// Handle the child scope beginning event to activate everything.
container.ChildLifetimeScopeBeginning += (sender, args) =>
  Activate(args.LifetimeScope.Resolve<IEnumerable<Meta<Lazy<IService>>>>());

using(var scope = container.BeginLifetimeScope("child"))
{
  // The named lifetime scope will kick off the event handler.
}

(Note I wrote that stuff off the top of my head. You may have to tweak it a bit, add error handling, etc.)

Working around it with events seems like more effort, but it means a couple of things:

1. You can do everything you need to right now with stuff that's already supported.
2. It'll work perfectly with registration sources and other dynamically registered things as long as they also include the appropriate metadata.

Something we could add, though, would be a "well known" metadata item on every registration that's registered using InstancePerMatchingLifetimeScope to include the set of tags. Then you wouldn't have to add the metadata yourself and would only have to add the event handler.

[tillig]

I added an extension method on IComponentRegistration to allow retrieval of matching lifetime scope tags for those components that have them. It'll be an empty enumeration if it's a singleton or otherwise doesn't have matching scope tags.