// called when the data is ready form facebook
        void photo_response(IDictionary<String, object> res)
        {
            object response;
            
            // getting all photos 
            if (res!= null && res.TryGetValue("data", out response))
            {
                foreach (JsonObject _post in (JsonArray)response)
                {
                    model = new FacebookItemViewModel(_post);
                    if (model.source_url != null)
                    {
                        // add album image source to allImages collection
                        AlbumImage image = new AlbumImage();
                        image.source_url = model.source_url;
                        hubTileUrl = model.source_url;
                        App.allImages.Add(image);
                     }                    
                }

                this.AllImagesListBox.ItemsSource = App.allImages;
            }
            else {
                    MessageBoxResult m = MessageBox.Show("Facebook null response", "Response", MessageBoxButton.OK);
                 }
        }
        void album_grp_response(IDictionary<String, object> res)
        {
            object response;

            // getting all photos 
            if (res.TryGetValue("data", out response))
            {
                foreach (JsonObject _post in (JsonArray)response)
                {
                    model = new FacebookItemViewModel(_post);
                    if (model.source_url != null)
                    {
                        AlbumImage image = new AlbumImage();
                        image.source_url = model.source_url;
                        App.albumImages.Add(image);
                    }
                }                
            }                  
         }