首先运行WPF动画，然后在Screen ViewModel中运行代码

<Window x:Class="MyApp.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="MyApp" Height="450" Width="800">
    <Grid>
        <Rectangle x:Name="myRectangle" Width="100" Height="100" Fill="Blue">
            <Rectangle.Triggers>
                <EventTrigger RoutedEvent="Loaded">
                    <BeginStoryboard>
                        <Storyboard>
                            <DoubleAnimation Storyboard.TargetName="myRectangle"
                                             Storyboard.TargetProperty="Opacity"
                                             From="1.0" To="0.0" Duration="0:0:1" AutoReverse="True" RepeatBehavior="Forever"/>
                        </Storyboard>
                    </BeginStoryboard>
                </EventTrigger>
            </Rectangle.Triggers>
        </Rectangle>
    </Grid>
</Window>

using System.Windows;
using System.Windows.Input;

namespace MyApp
{
    public class ScreenViewModel
    {
        public ICommand StartAnimationCommand { get; set; }
        public ICommand StopAnimationCommand { get; set; }

        public ScreenViewModel()
        {
            StartAnimationCommand = new RelayCommand(StartAnimation);
            StopAnimationCommand = new RelayCommand(StopAnimation);
        }

        private void StartAnimation()
        {
            // 在此处编写启动动画的代码
            // 例如，可以通过操作动画对象的属性来启动动画
            myRectangle.BeginAnimation(Rectangle.OpacityProperty, new DoubleAnimation(0.0, 1.0, TimeSpan.FromSeconds(1)));
        }

        private void StopAnimation()
        {
            // 在此处编写停止动画的代码
            // 例如，可以通过停止动画对象的属性来停止动画
            myRectangle.BeginAnimation(Rectangle.OpacityProperty, null);
        }
    }
}