Image binding from isolated storage? - silverlight

Question

I need some help to figure out why two different ways of binding an Image in XAML don't behave the same way.
Here is my code:
public class Picture
{
public int ID
{
get;
set;
}
public string ThumbURL
{
get
{
return String.Format("http://"+ App.ServerAdress +"/Pictures/thumbs/{0}.jpg", ID);
}
}
public int ThumbLocal
{
get { return ID; }
}
}
public class ByteImageConverter : IValueConverter
{
public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
{
using (var store =
IsolatedStorageFile.GetUserStoreForApplication())
{
if (!store.FileExists(value)) return null;
var stream =
store.OpenFile(path, FileMode.Open);
try
{
var image = new BitmapImage();
image.SetSource(stream);
return image;
}
finally
{
stream.Dispose();
}
}
}
public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
{
throw new NotImplementedException();
}
In case I bind the image this way, it is working:
<Image Width="110" CacheMode="BitmapCache" Source="{Binding ThumbURL}"
Margin="12,0,9,0"/>
But this way does not:
<Image Width="110" CacheMode="BitmapCache" Source="{Binding ThumbLocal, Mode=TwoWay, Converter={StaticResource imgConverter}}"
Margin="12,0,9,0"/>
This situation happens when I try to set picture from one panorama item to the other. I my case I want to add picture from one list to another and when I use first type of binding everything is working fine. Also it is working when I navigate to other page and navigate back, the picture shows up. I'm a little confused by this behavior.
Any ideas how I can solve this problem?
Finally I realized why this happened. Before Binding I have to download picture from the web and save it to the Isolated Storage, all this process is async. And in time when I Bind the picture there in no picture yet. I have try to Bind existing picture from Isolated Storage and it is correctly displayed. So, now I need something like INotifyPropertyChanged. Is any way I can do it if I use IValueConverter?

Answer 1

You can make it so that if the image is not in isolated storage - you start downloading the image, but return a new BitmapImage immediately and only when downloading is complete - save the image to isostore and set it as the BitmapImage's source.
Something like:
if (!store.FileExists(value))
{
var image = new BitmapImage();
ImageDownloadAndCachingHelper.DownloadImage(path, (s, e) => image.SetSource(e.ImageStream));
return image;
}
It is up to you to implement the code that converts the local path into a web URI, download it and invoke the EventHandler, where ImageDownloadedEventArgs has the ImageStream.