Public Shared Function ComparePartUri ( _
    firstPartUri As Uri, _
    secondPartUri As Uri _
) As Integer

Dim firstPartUri As Uri
Dim secondPartUri As Uri
Dim returnValue As Integer

returnValue = PackUriHelper.ComparePartUri(firstPartUri, _
    secondPartUri)

public static int ComparePartUri(
    Uri firstPartUri,
    Uri secondPartUri
)

public:
static int ComparePartUri(
    Uri^ firstPartUri, 
    Uri^ secondPartUri
)

public static function ComparePartUri(
    firstPartUri : Uri, 
    secondPartUri : Uri
) : int

You cannot use methods in XAML.