WPF打字机效果

    public partial class MainWindow : Window
    {
        public MainWindow()
        {
            InitializeComponent();
            TypewriteTextblock("我爱北京天安门,我爱祖国",this.TextBlockTest,new TimeSpan( *  * *));

        }
        private void TypewriteTextblock(string textToAnimate, TextBlock txt, TimeSpan timeSpan)
        {
            Storyboard story = new Storyboard();
            story.FillBehavior = FillBehavior.HoldEnd;
            story.RepeatBehavior = RepeatBehavior.Forever;

            DiscreteStringKeyFrame discreteStringKeyFrame;
            StringAnimationUsingKeyFrames stringAnimationUsingKeyFrames = new StringAnimationUsingKeyFrames();
            stringAnimationUsingKeyFrames.Duration = new Duration(timeSpan);

            string tmp = string.Empty;
            foreach (char c in textToAnimate)
            {
                discreteStringKeyFrame = new DiscreteStringKeyFrame();
                discreteStringKeyFrame.KeyTime = KeyTime.Paced;
                tmp += c;
                discreteStringKeyFrame.Value = tmp;
                stringAnimationUsingKeyFrames.KeyFrames.Add(discreteStringKeyFrame);
            }
            Storyboard.SetTargetName(stringAnimationUsingKeyFrames, txt.Name);
            Storyboard.SetTargetProperty(stringAnimationUsingKeyFrames, new PropertyPath(TextBlock.TextProperty));
            story.Children.Add(stringAnimationUsingKeyFrames);

            story.Begin(txt);
        }
    }