ExportFactory.cs

using System;
using System.Collections.Generic;
using System.ComponentModel.Composition;
using System.ComponentModel.Composition.Hosting;
using System.Linq;
using System.Text;

namespace MefDemo
{
    class Program
    {
        static void Main(string[] args)
        {
            var container = new CompositionContainer(
                new AssemblyCatalog(typeof(Program).Assembly)
                );
            var receiver = container.GetExport<TaskListener>();

            receiver.Value.Accept();
            receiver.Value.Accept();
            receiver.Value.Accept();

            Console.ReadKey();
        }
    }

    [Export]
    public class TaskListener
    {
        private readonly ExportFactory<TaskProcessor> taskProcessorFactory;

        [ImportingConstructor]
        public TaskListener(ExportFactory<TaskProcessor> taskProcessorFactory)
        {
            this.taskProcessorFactory = taskProcessorFactory;
        }

        public void Accept()
        {
            using (var processor = taskProcessorFactory.CreateExport())
            {
                processor.Value.Process();
            }
        }
    }

    [Export]
    public class TaskProcessor
    {
        private readonly DataContext dataContext;

        [ImportingConstructor]
        public TaskProcessor(DataContext dataContext)
        {
            Console.WriteLine("Ceated");
            this.dataContext = dataContext;
        }

        public void Process()
        {
            Console.WriteLine("Processing...");
        }
    }

    [Export]
    public class DataContext : IDisposable
    {
        public DataContext()
        {
            Console.WriteLine("Data context created");
        }

        public void Dispose()
        {
            Console.WriteLine("Data context disposed");
        }
    }
}