public interface IObjectResolver    {    }public class ObjectResolver:IObjectResolver    {      PRivate CompositionContainer container;      public ObjectResolver()      {          container = new CompositionContainer(new AggregateCatalog());      }      public void AddCatalogFile(string fileName)      {          if (!File.Exists(fileName))              throw new FileNotFoundException();          AggregateCatalog catalog = (AggregateCatalog)container.Catalog;          catalog.Catalogs.Add(new AssemblyCatalog(fileName));          container.ComposeParts();      }      public T GetExport<T>(string name)      {          return container.GetExportedValue<T>(name);      }    }