无法在WPF中为边距顶部设置动画

Question

我有一个名为MainStack的StackPanel。我正在尝试通过使用ThicknessAnimation设置其margin top属性的动画来垂直向下移动堆栈面板。老实说，我不知道为什么我的代码没有做任何事情。任何帮助，将不胜感激。

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;
using System.Windows.Media.Animation;

namespace casino
{

public partial class MainWindow : Window
{
    public MainWindow()
    {
        InitializeComponent();
    }

    private void Button_Click(object sender, RoutedEventArgs e)
    {
        ThicknessAnimation myThicknessAnimation = new ThicknessAnimation();
        myThicknessAnimation.Duration = TimeSpan.FromSeconds(5);
        myThicknessAnimation.FillBehavior = FillBehavior.HoldEnd;


        myThicknessAnimation.From = new Thickness(20, 20, 0, 0);
        myThicknessAnimation.To = new Thickness(20, 200, 0, 0);


        Storyboard.SetTargetName(myThicknessAnimation, "MainStack");
        Storyboard.SetTargetProperty(
            myThicknessAnimation, new 
            PropertyPath(Border.BorderThicknessProperty));

        Storyboard ellipseStoryboard = new Storyboard();
        ellipseStoryboard.Children.Add(myThicknessAnimation);

    }
}
}