C#のWPFでWaitingCircleコントロールを作る

<UserControl x:Class="WpfApplication1.WaitingCircle"
             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
             xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
             xmlns:local="clr-namespace:WpfApplication1"
             mc:Ignorable="d" 
             d:DesignHeight="300" d:DesignWidth="300">
    <Viewbox Stretch="Uniform">
        <Canvas x:Name="MainCanvas" Width="100" Height="100">
            <Canvas.RenderTransform>
                <RotateTransform x:Name="MainTrans" CenterX="50" CenterY="50"/>
            </Canvas.RenderTransform>
        </Canvas>
    </Viewbox>
</UserControl>

    public partial class WaitingCircle : UserControl
    {
        public static readonly DependencyProperty CircleColorProperty =
            DependencyProperty.Register(
                "CircleColor", // プロパティ名を指定
                typeof(Color), // プロパティの型を指定
                typeof(WaitingCircle), // プロパティを所有する型を指定
                new UIPropertyMetadata(Color.FromRgb(90, 117, 153),
                    (d, e) => {(d as WaitingCircle).OnCircleColorPropertyChanged(e); }));
        public Color CircleColor
        {
            get { return (Color)GetValue(CircleColorProperty); }
            set { SetValue(CircleColorProperty, value); }
        }


        public WaitingCircle()
        {
            InitializeComponent();

            double cx = 50.0;
            double cy = 50.0;
            double r  = 45.0;
            int    cnt = 14;
            double deg = 360.0 / (double)cnt;
            double degS = deg * 0.2;
            for (int i = 0; i < cnt; ++i)
            {
                var si1 = Math.Sin((270.0 - (double)i * deg) / 180.0 * Math.PI);
                var co1 = Math.Cos((270.0 - (double)i * deg) / 180.0 * Math.PI);
                var si2 = Math.Sin((270.0 - (double)(i + 1) * deg + degS) / 180.0 * Math.PI);
                var co2 = Math.Cos((270.0 - (double)(i + 1) * deg + degS) / 180.0 * Math.PI);
                var x1 = r * co1 + cx;
                var y1 = r * si1 + cy;
                var x2 = r * co2 + cx;
                var y2 = r * si2 + cy;

                var path = new Path();
                path.Data = Geometry.Parse(string.Format("M {0},{1} A {2},{2} 0 0 0 {3},{4}", x1, y1, r, x2, y2));
                path.Stroke = new SolidColorBrush(Color.FromArgb((byte)(255 - (i * 256 / cnt)), CircleColor.R, CircleColor.G, CircleColor.B));
                path.StrokeThickness = 10.0;
                MainCanvas.Children.Add(path);
            }

            var kf = new DoubleAnimationUsingKeyFrames();
            kf.RepeatBehavior = RepeatBehavior.Forever;
            for (int i = 0; i < cnt; ++i)
            {
                kf.KeyFrames.Add(new DiscreteDoubleKeyFrame()
                {
                    KeyTime = KeyTime.FromTimeSpan(TimeSpan.FromMilliseconds(i * 80)),
                    Value = i * deg
                });
            }
            MainTrans.BeginAnimation(RotateTransform.AngleProperty, kf);
        }

        public void OnCircleColorPropertyChanged(DependencyPropertyChangedEventArgs e)
        {
            if (null == MainCanvas) return;
            if (null == MainCanvas.Children) return;
            
            foreach (var child in MainCanvas.Children)
            {
                var shp = child as Shape;
                var sb  = shp.Stroke as SolidColorBrush;
                var a   = sb.Color.A;
                shp.Stroke = new SolidColorBrush(Color.FromArgb(a, CircleColor.R, CircleColor.G, CircleColor.B));
            }
        }
    }