async await、一歩一歩試用

 public   class downClass1

    {

     public  IStorageFile pResultStorageFile;

        public    async Task<IStorageFile> down()

        {      

            string CountriesFile = "fruit.xml";

           

 StorageFolder InstallationFolder =Windows.ApplicationModel.Package.Current.InstalledLocation;        

          StorageFile file = await InstallationFolder.CreateFileAsync(CountriesFile);

            BackgroundDownloader ppp = new BackgroundDownloader();

          DownloadOperation pDownloadOperation=  ppp.CreateDownload(new Uri("http://files.cnblogs.com/gisbeginner/fruit.xml"), file);
  await pDownloadOperation.StartAsync();

          pResultStorageFile = pDownloadOperation.ResultFile;

          return pResultStorageFile;         

            

        }

      

    }

}/// 

istorageFileタイプはTask〈istorageFile〉に返すことができ、このメソッドを呼び出すときIstorageFile pDownLoadFile=pdownClass 1.down() as IStorageFile; これじゃだめだ
public IStorageFile pDownLoadFile;
 pDownLoadFile =await  pdownClass1.down()、これでいいです
http://msdn.microsoft.com/en-us/library/hh191443(v=vs.110).aspx#Y749