windows phone richtextbox hyperlink remove underline

        private void AppendLink(string text, Uri uri)
        {
            Paragraph paragraph;
            if (this.Blocks.Count == 0 ||
                (paragraph = this.Blocks[this.Blocks.Count - 1] as Paragraph) == null)
            {
                paragraph = new Paragraph();
                this.Blocks.Add(paragraph);
            }
            var run = new Run { Text = processHTMLEntity(text.Replace("<em>", "").Replace("</em>", "")) };           
            run.Foreground = new SolidColorBrush(new Color() {A = 0xFF, R = 0x6a, G = 0x9b, B = 0xCD }); 
            var link = new Hyperlink { NavigateUri = uri };
            link.Inlines.Add(run);
            link.TextDecorations = null;
            link.Click += (sender, e) =>
                {
                    var lk = sender as Hyperlink;
                    new Microsoft.Phone.Tasks.WebBrowserTask() { Uri = lk.NavigateUri }.Show();
                };
            paragraph.Inlines.Add(link);
        }

link.TextDecorations = null; 即移除hyperlink的underline.