public async Task <byte[]> GetPictureBytesAsync(Uri uri)
{
string cacheFileName = MakeCacheFileName(uri);
var cacheddata = await FileCache.ReadItemBytesAsync(cacheFileName);
if (cacheddata != null)
{
return(cacheddata);
}
var webData = await WebApi.RequestDataAsync(uri);
await FileCache.WriteItemBytesAsync(cacheFileName, webData);
return(webData);
}