<Storyboard x:Name="TopOverlayIn">

      <DoubleAnimationUsingKeyFrames BeginTime="00:00:00" Storyboard.TargetName="TopOverlay"

          Storyboard.TargetProperty="(Canvas.Left)">

            <SplineDoubleKeyFrame KeyTime="00:00:01" Value="0"/>

      </DoubleAnimationUsingKeyFrames>

</Storyboard >

<Storyboard x:Name="TopOverlayOut">

      <DoubleAnimationUsingKeyFrames BeginTime="00:00:00" Storyboard.TargetName="TopOverlay"

          Storyboard.TargetProperty="(Canvas.Left)">

            <SplineDoubleKeyFrame KeyTime="00:00:01" Value="-325"/>

      </DoubleAnimationUsingKeyFrames>

</Storyboard >