using System;

using System.Collections.Generic;

using System.Linq;

public class Program

{

    public class Item

    {

        public int ID { get; set; }

        public string RegNo { get; set; }

        public string MobileNo { get; set; }

        public DateTime CreatedDate { get; set; }

    }

    public static void Main()

    {

        List<Item> Items = new List<Item>()

        {

            new Item { ID=26727  , RegNo=  "190076810", MobileNo ="9696562673" , CreatedDate= new DateTime(2017,2,13,6,31,0)},

            new Item { ID=26729  , RegNo=  "190123693", MobileNo ="9696562673" , CreatedDate= new DateTime(2017,2,13,6,35,0)},

            new Item { ID=45779  , RegNo=  "530087328", MobileNo ="5878525875" , CreatedDate= new DateTime(2017,2,7,7,23,0)},

            new Item { ID=99902  , RegNo=  "120058572", MobileNo ="7379130560" , CreatedDate= new DateTime(2017,2,8,12,39,0)},

            new Item { ID=64477  , RegNo=  "180073650", MobileNo ="7417516480" , CreatedDate= new DateTime(2017,2,10,13,47,0)},

            new Item { ID=81839  , RegNo=  "240087264", MobileNo ="7754990580" , CreatedDate= new DateTime(2017,2,11,10,47,0)}, 

        };

        var result = Items.GroupBy(x => x.MobileNo).Select(x => x.OrderByDescending(y => y.CreatedDate).First());

        foreach (Item item in result)

        {

            Console.WriteLine(string.Join(",", item.ID, item.RegNo, item.MobileNo, item.CreatedDate));

        }

    }

}