silverlight动画

 < Window
    xmlns= "http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x= "http://schemas.microsoft.com/winfx/2006/xaml"
    xml:lang= "zh-CN"
    xmlns:System= "clr-namespace:System;assembly=mscorlib"
    x:Name= "Window"
    Title= "Window1"
    Width= "640"  Height= "480">

    < Window.Resources>
        < Storyboard x:Key= "Timeline1"  RepeatBehavior= "Forever">
            < DoubleAnimationUsingKeyFrames BeginTime= "00:00:00"  
Storyboard.TargetName= "rectangle"  Storyboard.TargetProperty= "(Shape.strokeDashOffset)">
                < SplineDoubleKeyFrame KeyTime= "00:00:00"  Value= "100" />
                < SplineDoubleKeyFrame KeyTime= "00:00:00.5000000"  Value= "10" />
            < /DoubleAnimationUsingKeyFrames>
        < /Storyboard>
    < /Window.Resources>
    < Window.Triggers>
        < EventTrigger RoutedEvent= "FrameworkElement.Loaded"  SourceName= "rectangle">
            < BeginStoryboard Storyboard= "{StaticResource Timeline1}" />
        < /EventTrigger>
    < /Window.Triggers>

    < Grid x:Name= "LayoutRoot">
        < Grid Margin= "125,291,68"  VerticalAlignment= "Bottom"  Height= "113">
            < Rectangle Fill= "{x:Null}"  stroke= "#FF000000"  strokeDashCap= "Square"  
strokeDashOffset= "100"  strokeEndLineCap= "Square"  strokeLineJoin= "Miter"  
strokeStartLineCap= "Flat"  strokeThickness= "5"  x:Name= "rectangle">
                < Rectangle.strokeDashArray>
                    < System:Double>0< /System:Double>
                    < System:Double>2< /System:Double>
                < /Rectangle.strokeDashArray>
            < /Rectangle>
            < Button Margin= "2,2,2"  Content= "Button" />
        < /Grid>
    < /Grid>
< /Window>