using System.ComponentModel.Composition;
using Microsoft.Practices.Composite.Events;
 
//this version uses a static backing field so that the instance is automatically shared across all containers.
public class EventAggregatorPart
{
    private static IEventAggregator _eventAggregator;
 
    static EventAggregatorPart()
    {   
        _eventAggregator=new EventAggregator();
    }
 
    [Export]
    public IEventAggregator EventAggregator
    {
        get
        {
            return _eventAggregator;
        }
    }
}
 
//this version does not share the instance across containers.
public class EventAggregatorPart {
     [Export]
    public IEventAggregator EventAggregator
    {
        get
        {
            return new EventAggregator();        
        }
    }
}