Olostan

        private sealed class MyDumper
        {
            public static string Dump(Node root)
            {
                var sb = new StringBuilder();
                var workStack = new Stack<Helper>();
                workStack.Push(new Helper { Parent = null, CurrentNode = root, ParentIndent = string.Empty });
                while (workStack.Count > 0)
                {
                    Helper current = workStack.Pop();
                    if (current.Parent != null)
                    {
                        sb.Append(current.Parent.ParentIndent);
                        current.ParentIndent = current.Parent.ParentIndent +
                                               (current.IsLast ? " " : "│") +
                                               " ";
                        // my indent
                        sb.Append(current.IsLast ? "└" : "├");
                        sb.Append("-");
                    }
                    else current.ParentIndent = "";
                    sb.AppendLine(current.CurrentNode.Text);
                    for (int index = current.CurrentNode.Children.Count - 1; index >= 0; index--)
                    {
                        workStack.Push(new Helper
                                           {
                                               CurrentNode = current.CurrentNode.Children[index],
                                               Parent = current,
                                               IsLast = index == current.CurrentNode.Children.Count - 1
                                           });
                    }
                }
                return sb.ToString();
            }

            private class Helper
            {
                public bool IsLast;
                public Node CurrentNode;
                public Helper Parent;
                public string ParentIndent;
            }
        }