// sample for https://stackoverflow.com/questions/61395486/read-csv-file-and-return-indented-menu-c-sharp by sommmen

​

using System;

using System.Collections;

using System.Linq;

using System.Collections.Generic;

public class Program

{

    public class Node<T>

    {

        public T Data {get;set;}    

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

        public Node()

        {

            Children = new List<Node<T>>();

        }

        // Tree traversal in level order

         public List<Node<T>> LevelOrder()

        {

            List<Node<T>> list = new List<Node<T>>();

            Queue<Node<T>> queue = new Queue<Node<T>>();

            queue.Enqueue(this);

            while(queue.Count != 0)

            {               

                Node<T> temp = queue.Dequeue();

                foreach (Node<T> child in temp.Children)

                    queue.Enqueue(child);

                list.Add(temp);

            }

            return list;

        }

        public List<Node<T>> PreOrder()

        {

            List<Node<T>> list = new List<Node<T>>();

            list.Add(this);

            foreach (Node<T> child in Children)

                list.AddRange(child.PreOrder());

            return list;

        }

        public List<Node<T>> PostOrder()

        {

            List<Node<T>> list = new List<Node<T>>();

            foreach (Node<T> child in Children)

                list.AddRange(child.PreOrder());

            list.Add(this);

            return list;

        }

    }

    public class Entity

    {

        public int id   {get;set;}

        public string menuName {get;set;}

        public int? parentID {get;set;}

        public bool isHidden {get;set;}

        public string linkURL  {get;set;}

    }

    public static void Main()

    {

        var data = @"ID;MenuName;ParentID;isHidden;LinkURL

1;Company;NULL;False;/company

2;About Us;1;False;/company/aboutus

3;Mission;1;False;/company/mission

4;Team;2;False;/company/aboutus/team

5;Client 2;10;False;/references/client2

6;Client 1;10;False;/references/client1

7;Client 4;10;True;/references/client4

8;Client 5;10;True;/references/client5

10;References;NULL;False;/references";

        var lines = data.Split('\n');

        var rootNodes = new List<Node<Entity>>();

        var childItems = new List<Entity>();

        // Parse the data to entities

        // Items without a parent are used as rootnodes to build a tree

        foreach(var row in lines.Skip(1))

        {           

            var columns = row.Split(';');

            var id       = Convert.ToInt32(columns[0]);

            var menuName = columns[1];

            var parentID = ToNullableInt(columns[2]);

            var isHidden = Convert.ToBoolean(columns[3]);

            var linkURL  = columns[4];

            var entity = new Entity()

                              {

                                id = id,

                                  menuName = menuName,

                                  parentID = parentID,

                                  isHidden = isHidden,

                                  linkURL = linkURL

                              };

            if(parentID == null)

            {

                Console.WriteLine("Found root:" + entity.id + " - " + entity.menuName);

​

                rootNodes.Add(new Node<Entity>()

                              {

                                  Data = entity

                              });

            }

            else

            {

                childItems.Add(entity); 

            }

        }

        // Add the childElements to their appropriate rootnode

        foreach(var rootNode in rootNodes)

        {

            foreach(var childItem in childItems.OrderBy(a=>a.parentID).ThenBy(b=>b.menuName))

            {

                var newNode = new Node<Entity>()

                {

                    Data = childItem

                };

                Insert(rootNode, newNode);

            }

        }

        Console.WriteLine("-------------------");

        foreach(var rootNode in rootNodes)

        {

            var indent = 0;

            var previous = rootNode;

            foreach(var node in rootNode.LevelOrder())

            {

                if(node.Data.isHidden) continue;

                if(previous.Data.parentID != node.Data.parentID)

                    indent++;

                for(var i = 0; i < indent; i++)

                    Console.Write("\t");

                Console.WriteLine(node.Data.id + " - " + node.Data.menuName);

                previous = node;

            }

        }

    }

    public static void Insert(Node<Entity> rootNode, Node<Entity> targetNode)

    {

        foreach(var current in rootNode.LevelOrder())

        {

            if(current.Data.id == targetNode.Data.parentID)

            {

                current.Children.Add(targetNode);   

                return;

            }

        }

    }

    public static int? ToNullableInt(string s)

    {

        int i;

        if (int.TryParse(s, out i)) return i;

        return null;

    }

}