using System;

using System.Linq;

using System.Collections.Generic;

public class Program

{

    public static void Main()

    {

        var data = new List<Rooms>();

        data.AddRange(new List<Rooms>() { new Rooms() { Id = 0, Name = "Room", Code = "A" }, new Rooms() { Id = 998, Name = "Room", Code = "B" }, new Rooms() { Id = 59, Name = "Room", Code = "C" }, new Rooms() { Id = 62, Name = "Room CDE", Code = "D" }, new Rooms() { Id = 75, Name = "Room", Code = "E" },new Rooms() { Id = 80, Name = "Room", Code = "Z" },new Rooms() { Id = 10, Name = "Room ABC", Code = "R" } });

        //#1 - How many rooms are there?

        Console.WriteLine(data.Count());    

        //#2 - Store the room id #62 into a variable

        Rooms objRoom = data.Where(x=> x.Id == 62).FirstOrDefault();        

        if(objRoom != null) Console.WriteLine(objRoom.Id);

        //#3 - Group the rooms by Name and display the max id per each name group, ordered by name alphabetically

        IEnumerable<IGrouping<string, Rooms>> groups = data.GroupBy(x=> x.Name).ToList();

        Dictionary<string, List<Rooms>> dic = groups.ToDictionary(g=> g.Key, g=>g.ToList());

        foreach(KeyValuePair<string, List<Rooms>> kvp in dic)

        {

            Console.WriteLine(string.Format("Room Name : {0}, Max Id : {1}",kvp.Key, kvp.Value.Max(x=> x.Id)));

        }

    }

}

​

public class Rooms

{

    public int Id { get; set; }

    public string Name { get; set; }

    public string Code { get; set; }

}