Image Loading problem in Listbox, WP7

Question

I have a Listbox in which every element has an image that is already stored as content. I choose the image to be displayed using a converter.

If the image for the corresponding value does not exist, I have to display a default image which I have handled in the ImageFailed event.

The problem is that when I run the program I am getting the default image for a few images that already exist. If I scroll down the list box and back up again sometimes an image which was displayed properly displays the default image. This seems to be an performance issue.

I am new to application development, Let me know any detail even though it might seem trivial to you.

Below is my implementation

<ListBox DataContext="{Binding}">
    <ListBox.ItemTemplate>
        <DataTemplate>
                <StackPanel>
                            <Image Width="90" Height="67" Source="{Binding id,Converter={StaticResource imageConverter}}" ImageFailed="ImageFailed" />
                             _
                             _
                    </StackPanel>
        </DataTemplate>
    </ListBox.ItemTemplate>
</ListBox>

The convert function

public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
{
       string Id = (string)value;
   string imagePath;
   imagePath = string.Format(AppDefines.channelLogoImgPath, prgSvcId);
   return imagePath;
}

The ImageFailed handler

private void ImageFailed(object sender, ExceptionRoutedEventArgs e)
{
    Image Img = (Image)sender;
    string imgPath = Defines.defImagePath
    Uri uri = new Uri(imgPath, UriKind.RelativeOrAbsolute);
    BitmapImage bDefImage = new BitmapImage(uri);
    Img.Source = bDefImage;
}

Answer 1

The problem is that your convertor is returning a string (path to the image) and not an ImageSource.

You need something like this instead:

public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
{
   string imagePath = string.Format(AppDefines.channelLogoImgPath, value);
   return new BitmapImage(imagePath); 
} 

As Matt noted, you are also not using the id you are passing to the convertor. Simplified code above includes that fix.