c# WPF如何实现滚动显示的TextBlock

<UserControl x:Class="TestRoilingTextBlock.RoilingTextBlock"
             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
             xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
             DataContext="{Binding RelativeSource={RelativeSource Self}}"
             mc:Ignorable="d" d:DesignWidth="300" Height="136" Width="400">
    <UserControl.Template>
        <ControlTemplate TargetType="UserControl">
            <Border BorderBrush="Gray"
                    BorderThickness="1"
                    Padding="2"
                    Background="Gray">
                <Canvas x:Name="innerCanvas"
                        Width="Auto"
                        Height="Auto"
                        Background="AliceBlue"
                        ClipToBounds="True">
                    <TextBlock x:Name="textBlock"
                               Width="{Binding ActualWidth,ElementName=innerCanvas}" 
                               TextAlignment="Center"
                               TextWrapping="Wrap"
                               Height="Auto"
                               ClipToBounds="True"
                               Canvas.Left="{Binding Left,Mode=TwoWay}"
                               Canvas.Top="{Binding Top,Mode=TwoWay}"
                               FontSize="{Binding FontSize,Mode=TwoWay}"
                               Text="{Binding Text,Mode=TwoWay}"
                               Foreground="{Binding Foreground,Mode=TwoWay}">
 
                    </TextBlock>
                </Canvas>
 
            </Border>
        </ControlTemplate>
    </UserControl.Template>
</UserControl>

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;
using System.Windows.Threading;
 
namespace TestRoilingTextBlock
{
    /// <summary>
    /// RoilingTextBlock.xaml 的交互逻辑
    /// </summary>
    public partial class RoilingTextBlock : UserControl
    {
        private bool   canRoll = false;
        private double rollingInterval = 16;//每一步的偏移量
        private double offset=6;//最大的偏移量
        private TextBlock currentTextBlock = null;       
        private DispatcherTimer currentTimer = null;
        public RoilingTextBlock()
        {
            InitializeComponent();
            Loaded += RoilingTextBlock_Loaded;
        }
 
        void RoilingTextBlock_Loaded(object sender, RoutedEventArgs e)
        {
            if (this.currentTextBlock != null)
            {
                canRoll = this.currentTextBlock.ActualHeight > this.ActualHeight;
            }
            currentTimer = new System.Windows.Threading.DispatcherTimer();
            currentTimer.Interval = new TimeSpan(0, 0, 1);
            currentTimer.Tick += new EventHandler(currentTimer_Tick);
            currentTimer.Start();
        }
 
        public override void OnApplyTemplate()
        {
            try
            {
                base.OnApplyTemplate();
                currentTextBlock = this.GetTemplateChild("textBlock") as TextBlock;
            }
            catch (Exception ex)
            {               
               
            }
              
        }
 
        void currentTimer_Tick(object sender, EventArgs e)
        {
            if (this.currentTextBlock != null && canRoll)
            {
                if (Math.Abs(Top) <= this.currentTextBlock.ActualHeight-offset)
                {
                    Top-=rollingInterval;
                }
                else
                {
                    Top = this.ActualHeight;
                }
 
            }
        }
 
        #region Dependency Properties
        public static DependencyProperty TextProperty =
           DependencyProperty.Register("Text", typeof(string), typeof(RoilingTextBlock),
           new PropertyMetadata(""));
 
        public static DependencyProperty FontSizeProperty =
            DependencyProperty.Register("FontSize", typeof(double), typeof(RoilingTextBlock),
            new PropertyMetadata(14D));       
 
        public static readonly DependencyProperty ForegroundProperty =
           DependencyProperty.Register("Foreground", typeof(Brush), typeof(RoilingTextBlock), new FrameworkPropertyMetadata(Brushes.Green));
 
        public static DependencyProperty LeftProperty =
           DependencyProperty.Register("Left", typeof(double), typeof(RoilingTextBlock),new PropertyMetadata(0D));
 
        public static DependencyProperty TopProperty =
           DependencyProperty.Register("Top", typeof(double), typeof(RoilingTextBlock),new PropertyMetadata(0D));
     
        #endregion
 
        #region Public Variables
        public string Text
        {
            get { return (string)GetValue(TextProperty); }
            set { SetValue(TextProperty, value); }
        }
 
        public double FontSize
        {
            get { return (double)GetValue(FontSizeProperty); }
            set { SetValue(FontSizeProperty, value); }
        }
 
        public Brush Foreground
        {
            get { return (Brush)GetValue(ForegroundProperty); }
            set { SetValue(ForegroundProperty, value); }
        }
 
        public double Left
        {
            get { return (double)GetValue(LeftProperty); }
            set { SetValue(LeftProperty, value); }
        }
 
        public double Top
        {
            get { return (double)GetValue(TopProperty); }
            set { SetValue(TopProperty, value); }
        }
        #endregion
    }
}

<Window x:Class="TestRoilingTextBlock.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:local="clr-namespace:TestRoilingTextBlock"
        Title="MainWindow" Height="550" Width="525">
    <Grid>
        <local:RoilingTextBlock Foreground="Teal"
                                Text="汉皇重色思倾国，御宇多年求不得。杨家有女初长成，养在深闺人未识。天生丽质难自弃，一朝选在君王侧。回眸一笑百媚生，六宫粉黛无颜色。春寒赐浴华清池，温泉水滑洗凝脂。
                                侍儿扶起娇无力，始是新承恩泽时。云鬓花颜金步摇，芙蓉帐暖度春宵。春宵苦短日高起，从此君王不早朝。"
                                FontSize="22">           
        </local:RoilingTextBlock>
 
    </Grid>
</Window>