private void PreviousPieOnClick(object sender, MouseButtonEventArgs e)
        {
            if (PieView == null)
            {
                return;
            }
            var current = PieExamples.IndexOf(CartesianView);

            current--;
            PieView = current >= 0 ? PieExamples[current] : PieExamples[PieExamples.Count - 1];
        }
        private void NextPieOnClick(object sender, MouseButtonEventArgs e)
        {
            if (PieView == null)
            {
                return;
            }
            var current = PieExamples.IndexOf(CartesianView);

            current++;
            PieView = PieExamples.Count > current ? PieExamples[current] : PieExamples[0];
        }