Olostan

    static public string Dump(Node root)
    {
      return string.Join("",
        new[] { root.Text + "\n" }.Concat(
          root.Children.Take(root.Children.Count - 1).Select(Dump).Select(x => "├─" + x.TrimEnd().Replace("\n", "\n│ ")+"\n"))
          .Concat(root.Children.Skip(root.Children.Count - 1).Select(Dump).Select(x => "└─" + x.TrimEnd().Replace("\n", "\n ")+"\n"))
          .ToArray());
    }


    static public string Dump(Node root)
    {
      Func<Func<IEnumerable<Node>, int, IEnumerable<Node>>, string, string, Func<IEnumerable<Node>, IEnumerable<string>>> func =
        (take, a, b) => source => take(source, root.Children.Count - 1).Select(Dump)
          .Select(x => string.Format("{0}─{1}\n", a, x.TrimEnd().Replace("\n", "\n"+b+" ")));

      return string.Join("",
        new[] { root.
          Text + "\n" }.Concat(
          new []{func(Enumerable.Take,"├","│"),func(Enumerable.Skip,"└"," ")}.SelectMany(f => f(root.Children)))
          .ToArray());
    }