using System;

using System.Linq;

using System.Collections.Generic;

public class Host

{

        public string HostName { get; set; }

        public DateTime dt { get; set; }

}

​

public class Program

{

        static List<Host> GetServiceHosts(int days)

        {

            var list = new List<Host>() {

                new Host { HostName = "ServiceHostNameTest", dt = DateTime.Now.AddDays(-1 * days) },

                new Host { HostName = "ServiceHostNameTest", dt = DateTime.Now.AddDays(-1 * days - 1) },

                new Host { HostName = "servicehostNametest2", dt = DateTime.Now.AddDays(-1 * days) },

                new Host { HostName = "ServiceHostNameTest2", dt = DateTime.Now.AddDays(-1 * days - 1) },

                new Host { HostName = "BYAPHY101220913", dt = DateTime.Now.AddDays(-1 * days) },

                new Host { HostName = "BYAPHY101220913", dt = DateTime.Now.AddDays(-1 * days - 1) },

                new Host { HostName = "BYAPHY101220913", dt = DateTime.Now.AddDays(-1 * days - 1) }

            };

​

            return list;

        }

​

        public static void Main(string[] args)

        {

​

            var array = new[] { 1, 4, 8 };

​

            var result = array.SelectMany(item => GetServiceHosts(item))

                .GroupBy(host => host.HostName, StringComparer.OrdinalIgnoreCase)

                    .Select(hostGroup => hostGroup.OrderByDescending(host => host.dt).FirstOrDefault());

​

​

            Console.WriteLine(string.Join(", ", result.Select(x => string.Concat(x.HostName, "-", x.dt.ToString()))));

​

        }

}