How do you select the right size icon from a multi-resolution .ico file in WPF?

I use simple Markup Extension for that:

/// <summary>
/// Simple extension for icon, to let you choose icon with specific size.
/// Usage sample:
/// Image Stretch="None" Source="{common:Icon /Controls;component/icons/custom.ico, 16}"
/// Or:
/// Image Source="{common:Icon Source={Binding IconResource}, Size=16}"
/// </summary> 
public class IconExtension : MarkupExtension
{
    private string _source;

    public string Source
    {
        get
        {
            return _source;
        }
        set
        {
            // Have to make full pack URI from short form, so System.Uri recognizes it.
           _source = "pack://application:,,," + value;
        }
    }

    public int Size { get; set; }

    public override object ProvideValue(IServiceProvider serviceProvider)
    {
        var decoder = BitmapDecoder.Create(new Uri(Source), 
                                           BitmapCreateOptions.DelayCreation,
                                           BitmapCacheOption.OnDemand);

        var result = decoder.Frames.SingleOrDefault(f => f.Width == Size);
        if (result == default(BitmapFrame))
        {
            result = decoder.Frames.OrderBy(f => f.Width).First();
        }

        return result;
    }

    public IconExtension(string source, int size)
    {
        Source = source;
        Size = size;
    }

    public IconExtension() { }
}

Xaml usage:

<Image Stretch="None"
       Source="{common:Icon Source={Binding IconResource},Size=16}"/>

or

<Image Stretch="None"
       Source="{common:Icon /ControlsTester;component/icons/custom-reports.ico, 16}" />