public override void OnApplyTemplate()
{
base.OnApplyTemplate();
this.AddHandler(MouseDownEvent, new RoutedEventHandler((sender, e) =>
{
var targetHeight = Math.Max(ActualWidth, ActualHeight) * 2;
var mousePosition = (e as MouseButtonEventArgs).GetPosition(this);
var startMargin = new Thickness(mousePosition.X, mousePosition.Y, 0, 0);
var animation = GridContainer.FindResource("EllipseAnimation") as Storyboard;
//set initial margin to mouse position
Ellipse.Margin = startMargin;
//set the to value of the animation that animates the width to the target width
(animation.Children[0] as DoubleAnimation).To = targetHeight;
//set the to and from values of the animation that animates the distance relative to the container (grid)
(animation.Children[1] as ThicknessAnimation).From = startMargin;
(animation.Children[1] as ThicknessAnimation).To = new Thickness(mousePosition.X - targetHeight / 2, mousePosition.Y - targetHeight / 2, 0, 0);
Ellipse.BeginStoryboard(animation);
}), true);
}
