silverlight 实时更新 marquee效果

<Canvas x:Name="canMain" Background="Transparent" Cursor="Hand" >
                <Canvas.Clip>

                    <!--   定一个循环滚动的区域  -->
                    <RectangleGeometry x:Name="myRectangleGeometry" RadiusX="0" RadiusY="0" Rect="0,0, 340,50" />
                </Canvas.Clip>
                <Canvas.Triggers>
                    <EventTrigger RoutedEvent="Canvas.Loaded" >
                        <BeginStoryboard>

　　　　　　　　　　<!--  Canvas.Top :说明从下到上或者从上到下滚动 , RepeatBehavior="Forever" 为循环方式-->
                            <Storyboard x:Name="animation" Storyboard.TargetProperty="(Canvas.Top)" RepeatBehavior="Forever" >
                                <DoubleAnimation x:Name="daOne" Storyboard.TargetName="spScrollTwo" From="0" To="0" Duration="0:0:10"  />
                                <DoubleAnimation x:Name="daTwo" Storyboard.TargetName="spScrollOne" From="0" To="0" Duration="0:0:10"  />
                            </Storyboard>
                        </BeginStoryboard>
                    </EventTrigger>
                </Canvas.Triggers>
                <StackPanel x:Name="spScrollOne" Orientation="Vertical"></StackPanel> >//要滚动的集合一
                <StackPanel x:Name="spScrollTwo" Orientation="Vertical"></StackPanel>//要滚动的集合二
            </Canvas>

// 这里我采用的是后台动态赋值:

public partial class testScroll: UserControl
    {

         // 信息条数
        int icount = 0;

  // 信息显示高度
        Double iRoadInforMation = 0;

        public testScroll()
        {
            InitializeComponent();
            this.Loaded += new RoutedEventHandler(testScroll_Loaded);
        }

        #region 页面初始化方法
        /// <summary>
        /// 页面初始化方法
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        void testScroll_Loaded(object sender, RoutedEventArgs e)
        {
            //动态获取数据

            getDataInfor();

        DispatcherTimer dt;
            //定义计时器       
            dt = new DispatcherTimer()
            {
                Interval = TimeSpan.FromMinutes(3)
            };
            dt.Tick += (sen, sec) =>
            {
                getDataInfor();
            };
            dt.Start();
        }
        #endregion

 #region 获得信息
        /// <summary>
        /// 获得信息
        /// </summary>
        private void getDataInfor()
        {
                ......  ......... // 连接数据库

                 //  返回成功信息
                if (r.IsSucceed)
                {
                    //  定义实体类的集合
                     List<R_Infor>  _Data_InforList = r.Body.FromJsonString<List<R_Infor>>();

                    //  判断返回查询结果
                    if (null != _Data_InforList && 0 < _Data_InforList .Count)
                    {
                        //  根据查询信息给页面赋值
                        foreach (var _Infor in_Data_InforList )
                        {

　　　　　　　　　　
                            double _fontsize = 15;
                            ++icount;

                            // 定义页面滚动显示信息容器
                            var tbInforOne = new TextBlock();
                            // 设定显示信息的样式信息
                            tbInforOne .Text = icount + ". " +  _Infor .nayiyaou(); //描述内容
                            tbInforOne .Tag =Infor .ID();//内容ID
                            tbInforOne .FontSize = _fontsize;
                            tbInforOne .LineHeight = _fontsize;
                            tbInforOne .TextWrapping = TextWrapping.Wrap; //自动换行
                            tbInforOne .Margin = new Thickness(3, 4, 3, 3); //位置
                            tbInforOne .Width = (double)325; //显示宽度
                             spScrollOne.Children.Add(tbTraInforOne); //显示添加上前台控件
                            iRoadInforMation += (tbInforOne .ActualHeight + 7); //获得实际显示高度

                            // 定义页面滚动显示信息容器
                            var tbInforTwo = new TextBlock();

                             tbInforTwo .Text = icount + ". " +  _Infor .nayiyaou(); //描述内容
                            tbInforTwo .Tag =Infor .ID();//内容ID
                            tbInforTwo .FontSize = _fontsize;
                            tbInforTwo .LineHeight = _fontsize;
                            tbInforTwo .TextWrapping = TextWrapping.Wrap; //自动换行
                            tbInforOne .Margin = new Thickness(3, 4, 3, 3); //位置
                            tbInforTwo .Width = (double)325; //显示宽度
                               spScrollTwo.Children.Add(tbTraInforTwo);

                        }
                        setScrolltt();
                    }
                }
            };
            _Do.Post();
        }
        #endregion

 #region 设置滚动信息
        /// <summary>
        /// 设置滚动信息
        /// </summary>
        private void setScrolltt()
        {
            iRoadInforMation = iRoadInforMation + 10;
            myRectangleGeometry.Rect = new Rect(0, 0, 340, iRoadInforMation);
            // 控制滚动信息速度
            int _marqueeTimeInSeconds = Convert.ToInt32(icount * 1.5);
            spScrollOne.Height = iRoadInforMation;
            spScrollTwo.Height = iRoadInforMation;
            daOne.To = -iRoadInforMation;
            daOne.Duration = new Duration(TimeSpan.FromSeconds(_marqueeTimeInSeconds));
            daTwo.From = iRoadInforMation;
            daTwo.Duration = new Duration(TimeSpan.FromSeconds(_marqueeTimeInSeconds));

     animation.Begin();
            // 判断是否定制滚动信息
            if (canMain.ActualHeight >= spScrollOne.Height)
            {
                animation.Stop();
                return;
            }
        }
        #endregion

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