using System;

using System.Linq;

using System.Collections.Generic;

public class Program

{

    public static void Main()

    {

        var list = new List<RoomDetails>

        {

            new RoomDetails(1,1,200,"SingleBed"),

            new RoomDetails(2,1,250,"Double Bed"),

            new RoomDetails(2,2,400,"Double Bed with Extra View"),

            new RoomDetails(2,4,530,"Tripple Bed"),

            new RoomDetails(3,1,530,"Tripple Bed"),

            new RoomDetails(3,2,600,"Triple Large Bed"),

        };

        var total = list.GroupBy(x=>x.RoomIndexID)

            .Select(x=>x.Count())

            .Aggregate(1, (s,d)=>s*d);

        var counts = list.GroupBy(x => x.RoomIndexID)

            .ToDictionary(x => x.Key, x => x.Count());

        var nums = list.GroupBy(x => x.RoomIndexID)

            .Select(x => x.Select((p, i) => new {i, p}))

            .SelectMany(x => x)

            .ToList();

        var result = Enumerable.Range(0, total)

            .Select(x =>

                nums.Where(y => {               

                    var c = counts[y.p.RoomIndexID];

                    var p = counts.Where(z => z.Key > y.p.RoomIndexID).Aggregate(1, (s,d)=>s*d.Value);

                    return y.i == x/p%c;

                })

                .Select(y => y.p)

            );

        foreach(var r in result)

        {

            foreach(var rm in r)

            {

                Console.WriteLine(rm);

            }

            Console.WriteLine("==================================");

        }

    }

}

​

class RoomDetails

{

    public RoomDetails(int roomIndexID, int roomcategoryID, decimal roomPrice, string roomCategory)

    {

        this.RoomIndexID = roomIndexID;

        this.roomcategoryID = roomcategoryID;

        this.roomPrice = roomPrice;

        this.roomCategory = roomCategory;

    }

     public int RoomIndexID { get; set; }

     public int roomcategoryID { get; set; }

     public decimal roomPrice { get; set; }

     public string roomCategory { get; set; }

​

    public override string ToString()

    {

        return string.Format("{0}, {1}, {2}, {3}", RoomIndexID, roomcategoryID, roomPrice, roomCategory);

    }

}