画一条直线，实现直线流动显示，线段一段流向另一端的控制怎么实现

前台

 <esri:SimpleLineSymbol x:Key="RouteRenderer" Style="DashDotDot" >
                <esri:LineSymbol.ControlTemplate>
                    <ControlTemplate>
                        <Grid>
                            <VisualStateManager.VisualStateGroups>
                                <VisualStateGroup x:Name="CommonStates">
                                    <VisualState x:Name="Normal">
                                        <Storyboard  RepeatBehavior="Forever"   >
                                            <DoubleAnimation  BeginTime="0:0:0" RepeatBehavior="3x"  From="50"  
                                                              AutoReverse="True"  Storyboard.TargetName="Element" 
                                                              Storyboard.TargetProperty="StrokeDashOffset"  To="500" Duration="0:3:0" />
                                        </Storyboard>
                                    </VisualState>
                                </VisualStateGroup>
                            </VisualStateManager.VisualStateGroups>
                            <Path x:Name="Element" StrokeDashArray="1,2" StrokeDashOffset="0" Stroke="#990000FF" StrokeThickness="8" />
                        </Grid>
                    </ControlTemplate>
                </esri:LineSymbol.ControlTemplate>
            </esri:SimpleLineSymbol>

后台是Draw画的