If what you are trying to achieve is navigate to another page when you tap on an item you should just register for the Tap event inside your Item DataTemplate and in the event handler do something like this:
Private Sub Item_Tap(sender As Object, e As GestureEventArgs)
Dim element As FrameworkElement = TryCast(sender, FrameworkElement)
Dim item As JumpDemo = TryCast(element.DataContext, JumpDemo)
Dim addressString As String = item.Link
Dim pageUri As Uri = New Uri(addressString, UriKind.Relative)
NavigationService.Navigate(pageUri)
End Sub