WPF:如何在MVVM中播放故事板？

public class MainViewModel : INotifyPropertyChanged
{
    private bool _isPlaying;

    public bool IsPlaying
    {
        get { return _isPlaying; }
        set
        {
            _isPlaying = value;
            OnPropertyChanged("IsPlaying");
        }
    }

    public event PropertyChangedEventHandler PropertyChanged;

    protected virtual void OnPropertyChanged(string propertyName)
    {
        PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
    }
}

        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        xmlns:local="clr-namespace:WpfApp1"
        mc:Ignorable="d"
        Title="MainWindow" Height="450" Width="800">
   <Window.DataContext>
       <local:MainViewModel/>
    </Window.DataContext>
    <Grid>
       <Button Content="Play" IsEnabled="{Binding IsPlaying, Converter={StaticResource BooleanInverter}}"/>
       <Button Content="Pause" IsEnabled="{Binding IsPlaying}"/>
    </Grid>
</Window>

   <DoubleAnimation Storyboard.TargetProperty="Opacity" From="1" To="0" Duration="0:0:1"/>
</Storyboard>

    <i:Interaction.Triggers>
        <i:EventTrigger EventName="Click">
            <i:InvokeCommandAction Command="{Binding PlayCommand}"/>
        </i:EventTrigger>
    </i:Interaction.Triggers>
   <Button.Style>
       <Style TargetType="Button">
           <Style.Triggers>
                <DataTrigger Binding="{Binding IsPlaying}" Value="True">
                    <DataTrigger.EnterActions>
                       <BeginStoryboard Storyboard="{StaticResource PlayPauseStoryboard}"/>
                    </DataTrigger.EnterActions>
                </DataTrigger>
            </Style.Triggers>
        </Style>
    </Button.Style>
</Button>