使用DataTrigger启动Storyboard

Question

我想用Datatrigger开始一个Storyboard。现在我有一个适合我的Eventtrigger解决方案。这是我的代码：

<Rectangle Width="100" Height="100">
    <Rectangle.Fill>
        <ImageBrush x:Name="test" ImageSource="Tulips.jpg"></ImageBrush>
    </Rectangle.Fill>      
    <Rectangle.Triggers>
        <EventTrigger RoutedEvent="Rectangle.Loaded">
            <BeginStoryboard>
                <Storyboard>
                    <ObjectAnimationUsingKeyFrames 
                        Storyboard.TargetProperty="(ImageSource)" 
                        Storyboard.TargetName="test">
                        <DiscreteObjectKeyFrame KeyTime="0:0:1">
                            <DiscreteObjectKeyFrame.Value>
                                <BitmapImage UriSource="Tulips.jpg" />
                            </DiscreteObjectKeyFrame.Value>
                        </DiscreteObjectKeyFrame>
                        <DiscreteObjectKeyFrame KeyTime="0:0:2">
                            <DiscreteObjectKeyFrame.Value>
                                <BitmapImage UriSource="Chrysanthemum.jpg" />
                            </DiscreteObjectKeyFrame.Value>
                        </DiscreteObjectKeyFrame>
                     </ObjectAnimationUsingKeyFrames>
                </Storyboard>
            </BeginStoryboard>
        </EventTrigger>
    </Rectangle.Triggers>
</Rectangle>

现在，如果Code Behind File中的变量设置为特定值，我想用数据触发器启动故事板。我怎么能这样做？