using System;

using System.Collections.Generic;

public class Program

{

    public static void Main()

    {

        Node root = new Node(

            new List<Node>() {

                new Node(new List<Node>() {

                    new Node(null, "1.1"),

                    new Node(null, "1.2")

                }, "1"),

                new Node(new List<Node>() {

                    new Node(null, "2.1")

                }, "2")

            },

            "root"

        );

        IEnumerable<string> inOrderValues = PreOrderValues(root);

        foreach (var inOrderValue in inOrderValues) {

            Console.WriteLine(inOrderValue);    

        }

        Console.WriteLine("---");

        IEnumerable<string> postOrderValues = PostOrderValues(root);

        foreach (var postOrderValue in postOrderValues) {

            Console.WriteLine(postOrderValue);  

        }

    }

    public static IEnumerable<string> PreOrderValues(Node node) {

    }

    public static IEnumerable<string> PostOrderValues(Node node) {

    }

}

​

public class Node {

    public List<Node> Children { get; set; }

    public string Value { get; set; }

    public Node(List<Node> children, string value) {

        this.Children = children != null ? children : new List<Node>();

        this.Value = value;

    }

}

​