Get strings from TextBlock

this.TextBlock.Width = document.CurrentPage.Content.ActualWidth;
this.TextBlock.Measure(new Size(double.PositiveInfinity, double.PositiveInfinity));

Window w = new Window();
w.Content = this.TextBlock;
w.Show();

Drawing textBlockDrawing = VisualTreeHelper.GetDrawing(this.TextBlock);
List<String> list = new List<String>();
WalkDrawingForText(list, textBlockDrawing);

private static void WalkDrawingForText(List<String> list, Drawing d)
{
    var glyphs = d as GlyphRunDrawing;
    if (glyphs != null)
    {
        list.Add(new string(glyphs.GlyphRun.Characters.ToArray()));
    }
    else
    {
        var g = d as DrawingGroup;
        if (g != null)
        {
            foreach (Drawing child in g.Children)
            {
                WalkDrawingForText(sb, child);
            }
        }
    }
}