private IEnumerable <Lazy <T> > GetExportsCore <T>(string contractName)
        {
            IEnumerable <Export> exports = this.GetExportsCore(typeof(T), (Type)null, contractName, ImportCardinality.ZeroOrMore);

            Collection <Lazy <T> > result = new Collection <Lazy <T> >();

            foreach (Export export in exports)
            {
                result.Add(ExportServices.CreateStronglyTypedExportOfT <T>(export));
            }
            return(result);
        }
        private Lazy <T> GetExportCore <T>(string contractName)
        {
            Export export = this.GetExportsCore(typeof(T), null, contractName, ImportCardinality.ExactlyOne).SingleOrDefault();

            return((export != null) ? ExportServices.CreateStronglyTypedExportOfT <T>(export) : null);
        }