Windows Phone 7导航动画

我试图在离开页面时制作动画,但得到以下错误:

无法解析指定对象上的TargetProperty(uiElement.renderTransform)。(CompositeTransform.TranslateX)。

我从一本书中复制了代码,我测试了这本书的样本代码,它可以工作,但我不能让它在我的应用程序上工作。有什么想法吗?这是我的代码:

XAML:

<phone:PhoneApplicationPage.Resources>
        <Storyboard x:Name="HidePage" Completed="HidePage_Completed">
            <DoubleAnimationUsingKeyFrames Storyboard.TargetProperty="(UIElement.RenderTransform).(CompositeTransform.TranslateX)" Storyboard.TargetName="phoneApplicationPage">
                <EasingDoubleKeyFrame KeyTime="0" Value="0"/>
                <EasingDoubleKeyFrame KeyTime="0:0:1" Value="-480"/>
            </DoubleAnimationUsingKeyFrames>
            <DoubleAnimationUsingKeyFrames Storyboard.TargetProperty="(UIElement.RenderTransform).(CompositeTransform.TranslateY)" Storyboard.TargetName="phoneApplicationPage">
                <EasingDoubleKeyFrame KeyTime="0" Value="0"/>
                <EasingDoubleKeyFrame KeyTime="0:0:1" Value="-800"/>
            </DoubleAnimationUsingKeyFrames>
        </Storyboard>
<phone:PhoneApplicationPage.Resources>

C.*

protected override void OnNavigatingFrom(NavigatingCancelEventArgs e)
{
    base.OnNavigatingFrom(e);

    if (this.UriToNavigateTo == null)
    {
        e.Cancel = true;
        UriToNavigateTo = e.Uri;
        this.HidePage.Begin();
    }
    else
    {
        UriToNavigateTo = null;
    }
}

谢谢!