Public Shared Function ComparePackUri ( _
    firstPackUri As Uri, _
    secondPackUri As Uri _
) As Integer

Dim firstPackUri As Uri
Dim secondPackUri As Uri
Dim returnValue As Integer

returnValue = PackUriHelper.ComparePackUri(firstPackUri, _
    secondPackUri)

public static int ComparePackUri(
    Uri firstPackUri,
    Uri secondPackUri
)

public:
static int ComparePackUri(
    Uri^ firstPackUri, 
    Uri^ secondPackUri
)

public static function ComparePackUri(
    firstPackUri : Uri, 
    secondPackUri : Uri
) : int

You cannot use methods in XAML.