Public Shared Sub SetDesiredFrameRate ( _
    timeline As Timeline, _
    desiredFrameRate As Nullable(Of Integer) _
)

Dim timeline As Timeline
Dim desiredFrameRate As Nullable(Of Integer)

Timeline.SetDesiredFrameRate(timeline, _
    desiredFrameRate)

public static void SetDesiredFrameRate(
    Timeline timeline,
    Nullable<int> desiredFrameRate
)

public:
static void SetDesiredFrameRate(
    Timeline^ timeline, 
    Nullable<int> desiredFrameRate
)

public static function SetDesiredFrameRate(
    timeline : Timeline, 
    desiredFrameRate : Nullable<int>
)

You cannot use methods in XAML.