Is there a good way to use events with Unity?

Question

programAction = UnityContainer.Resolve<LoaderDriver>();
(programAction as LoaderDriver).LoadComplete +=
    new EventHandler(Program_LoadComplete);

Is there a configuration that let's me resolve my objects having already been wired to an event?

Alternately, is there a preferred way to achive the same result? I've noticed that sometimes when I don't see a "feature" its because a pattern I don't know about is preferred.

Answer 1

Yes there is a way. You would have to write an extension that adds a custom BuilderStrategy to the PostInitialization stage of the Unity BuildPipeline.

The code for extension and strategy should look similar to this:

public class SubscriptionExtension : UnityContainerExtension
{
  protected override void Initialize()
  {
    var strategy = new SubscriptionStrategy();
    Context.Strategies.Add(strategy, UnityBuildStage.PostInitialization);
  }
}
public class SubscriptionStrategy : BuilderStrategy
{
  public override void PostBuildUp(IBuilderContext context)
  {
    if (context.Existing != null)
    {
      LoaderDriver ld = context.Existing as LoaderDriver;
      if(ld != null)
      {
        ld.LoadComplete += Program_LoadComplete;
      }
    }
  }
}

Then you add the extension to the container

container.AddNewExtension<SubscriptionExtension>();

And when you resolve your LoaderDriver instance it will automatically subscribe to the EventHandler.

You can find a working sample that subscribes classes to an EventAggregator in the TecX project. The source code is located in the TecX.Event.Unity project.

Answer 2

I wrote a Unity Event Broker that you might find useful. See this post.