Olostan

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