/// <summary>
 /// This method visualizes the placeholder state of the data item. When 
 /// showing a placehlder, we set the opacity of other elements to zero
 /// so that stale data is not visible to the end user.  Note that we use
 /// Grid's background color as the placeholder background.
 /// </summary>
 /// <param name="item"></param>
 public void ShowPlaceholder(Item item)
 {
     _item = item;
     titleTextBlock.Opacity = 0;
     categoryTextBlock.Opacity = 0;
     image.Opacity = 0;
 }
        /// <summary>
        /// This method shows the Title of the data item as well as a placholder
        /// for the image. We set the opacity of other UIElements to zero
        /// so that stale data is not visible to the end user.  Note that we use
        /// Border's background color as the image placeholder.
        /// </summary>
        /// <param name="item"></param>
        public void ShowTitle(Item item)
        {
            _item = item;
            subtitleTextBlock.Opacity = 0;
            image.Opacity = 0;

            titleTextBlock.Text = _item.Title;
            titleTextBlock.Opacity = 1; 
        }