using System;

using System.Collections.Generic;

using System.Text;

public class Program

{

    public static void Main()

    {

        var root = new Thing{Id = 1,Name = "Thing1"};       

        var thing2 = new Thing{Id = 2,Name = "Thing2"};             

        var thing3 = new Thing{Id = 3,Name = "Thing3"};     

        root.children.Add(thing2);

        thing2.children.Add(thing3);                                      

        thing3.children.Add(root);          

        Console.WriteLine(root.ToString());     

    }

}

​

public class Thing

{

    public int Id {get; set;}

    public string Name {get; set;}

    public List<Thing> children{ get; set;} 

    public Thing()

    {

        this.children = new List<Thing>();

    }

    public string ToString(int level = 0)

    {

        var sb = new StringBuilder();

        sb.Append(new String('-',level));

        sb.AppendLine($"id:{Id} Name:{Name}");          

        foreach(var child in children)

        {

            sb.Append(child.ToString(level + 1));

        }       

        return sb.ToString();

    }

}