ColorAnimation silverlight跑马灯效果

前台代码：

<UserControl x:Class="story.MainPage"
    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="@L_502_3@"
    mc:Ignorable="d"
    d:DesignHeight="300" d:DesignWidth="400">
    <UserControl.Resources >
        <Storyboard  x:Name="sb">
            <ColorAnimation Storyboard.TargetName="scBrush" Storyboard.TargetProperty="Color" From="Red" To="White" Duration="00:00:1" RepeatBehavior="Forever" ></ColorAnimation>
        </Storyboard>
        <Storyboard x:Name="sb2">
            <DoubleAnimation  Storyboard.TargetName="gd1" Storyboard.TargetProperty="Offset" From="0" To="1" Duration="00:00:1" RepeatBehavior="Forever" >
               
            </DoubleAnimation>
        </Storyboard>
    </UserControl.Resources>
        <Grid x:Name="LayoutRoot" Background="White">
        <StackPanel  Width="300" Height="300">
            <Ellipse Width="100" Height="100" Name="el1">
                <Ellipse.Fill >
                    <SolidColorBrush x:Name="scBrush"></SolidColorBrush>
                </Ellipse.Fill>
            </Ellipse>
            <TextBlock Name="tb1" Width="200" Height="28" FontSize="24" Text="我在，世界在......">
              <TextBlock.Foreground >
                  <LinearGradientBrush x:Name="lb1">
                     <GradientStop Offset="0" Color="Black" ></GradientStop>
                      <GradientStop Offset="0.5" Color="Yellow"  x:Name="gd1" ></GradientStop>
                      <GradientStop Offset="1" Color="Black" ></GradientStop>
                  </LinearGradientBrush>
              </TextBlock.Foreground>
            </TextBlock>
            <Button Content="开始" Height="23" HorizontalAlignment="Left"  VerticalAlignment="Bottom" Name="button1"  Width="75" Click="button1_Click" />
        </StackPanel>
           
       
    </Grid>
</UserControl>

后台代码：

 private void button1_Click(object sender,RoutedEventArgs e)         {             sb.Begin();             sb2.Begin();         }