private void btnResizeTo_Click(object sender, RoutedEventArgs e)
{
var rect = new Rectangle()
{
Height = 250,
Width = 350,
Fill = new SolidColorBrush(Colors.Blue)
};
MainStage.Children.Add(rect);
rect.SetPosition(50, 50);
rect.ResizeTo(150, 150, 1.5.seconds())
.WhenComplete(a =>
{
Thread.Sleep(2000);
MainStage.Children.Remove(rect);
})
.Begin();
}