private async Task saveImageToDisk(Articolo art) // async
		{
			HttpClient c = new HttpClient();
			c.BaseAddress =  new Uri(art.UrlImg);
			c.Timeout = new TimeSpan(0,0, 3);

			Byte[] imgByteArray = await c.GetByteArrayAsync ("");

			CancellationToken a = new CancellationToken();

			IFolder rootFolder = FileSystem.Current.LocalStorage;
  
			IFolder folder = await rootFolder.CreateFolderAsync("Immagini",
				CreationCollisionOption.OpenIfExists);

			var listaFilePerVerifica = await folder.GetFilesAsync (new CancellationToken ());

			var listafile = await folder.GetFilesAsync ();
			
			IFile file = await folder.CreateFileAsync(art.ImageFileName ,
				CreationCollisionOption.ReplaceExisting);
  
			// http://www.mallibone.com/post/storing-files-from-the-portable-class-library-(pcl)

			using (var fileHandler = await file.OpenAsync (FileAccess.ReadAndWrite)) {
				fileHandler.WriteAsync(imgByteArray, 0, imgByteArray.Length); // await
			}   
		}
		public int SaveItem (Articolo item) 
		{
			lock (locker) {
				if (item.Id != 0) {
					database.Update(item);
					return item.Id;
				} else {
					return database.Insert(item);
				}
			}
		}
 public DetaglioPage(Articolo articolo)
 {
     _articolo = articolo;
     InitializeComponent ();
     Title = articolo.art_DESC;
 }