come posso applicare il seguente effetto ad una window wpf anzichè a Rectangle1

codice:
           'avvia l'animazione dei rectangle
            Dim myStoryboard As New Storyboard
            Dim myDoubleAnimation As DoubleAnimation = New DoubleAnimation()
            myDoubleAnimation.From = 1.0
            myDoubleAnimation.To = 0.0
            myDoubleAnimation.Duration = New Duration(TimeSpan.FromSeconds(1))
            myDoubleAnimation.AutoReverse = False
            'myDoubleAnimation.RepeatBehavior = RepeatBehavior.Forever
            myStoryboard = New Storyboard()
            myStoryboard.Children.Add(myDoubleAnimation)
            Storyboard.SetTargetName(myDoubleAnimation, Me.Rectangle1.Name)
            Storyboard.SetTargetProperty(myDoubleAnimation, New PropertyPath(Rectangle.OpacityProperty))
            myStoryboard.Begin(Me)