using System;

using System.Collections.Generic;

using System.Collections.Immutable;

using System.Linq;

​

public sealed class Program

{

    public sealed class Node

    {

        private readonly string name;

​

        public Node(string name)

            : this(name, Array.Empty<string>())

        {

        }

​

        public Node(string name, params string[] childNodes)

            : this(name, childNodes.Select(s => new Node(s)).ToImmutableList())

        {

        }

​

        private Node(string name, IEnumerable<Node> childNodes)

        {

            this.name = name;

            ChildNodes = childNodes;

        }

​

        public IEnumerable<Node> ChildNodes { get; }

​

        public override string ToString()

        {

            return $"{nameof(name)}: {name}";

        }

    }

​

    private static IEnumerable<Node> Nodes { get; } = new[]

    {

        new Node("image", "raw", "jpeg", "png"),

        new Node("video", "mp4"),

        new Node("game"),

        new Node("music", "wav", "mp3"),

    };

​

    private static void FixMe()

    {

        var list = Nodes.SelectMany(n => n.ChildNodes.Take(1));

        foreach (var n in list)

        {

            Console.WriteLine(n);

        }

    }

​

    public static void Main(string[] args)

    {

        FixMe();

    }

}

​