Prism’s event aggregator is great for decoupling UI state changes when UI events occur, but sometimes you need to perform some larger, long-running task on a background thread — uploading a file, for example.
Here’s a quick example of an encapsulated event handler listening off the Prism event bus, and using Windsor’s IStartable facility to handle event subscription:
public class TradeCancelledEventHandler : ICompositePresentationEventHandler, IStartable{ private readonly IEventAggregator eventAggregator; protected TradeCancelledEventHandler(IEventAggregator eventAggregator) { if (eventAggregator == null) throw new ArgumentNullException("eventAggregator"); this.eventAggregator = eventAggregator; } public void Start() { // Register to receive events on the background thread eventAggregator .GetEvent<TradeCancelledEvent>() .Subscribe(Handle, ThreadOption.BackgroundThread); } public void Stop() { eventAggregator .GetEvent<TradeCancelledEvent>() .Unsubscribe(Handle); } void Handle(TradeCancelledEventArgs eventArgs) { // ... do stuff with the event }} Each event handler is effectively a little service running in the container. Note ICompositePresentationEventHandler is a simple role interface that allows us to register them all at once in the IoC container:
public interface ICompositePresentationEventHandler {}...container.AddFacility<StartableFacility>();// Register event handlers in containercontainer.Register( AllTypes .Of<ICompositePresentationEventHandler>() .FromAssembly(Assembly.GetExecutingAssembly()));
