using System;

using System.Linq;

using System.Collections.Generic;

public class Program

{

    public static void Main()

    {

        List<RoutingData> savedMessages = new List<RoutingData>();

        List<RoutingData> incomingMessages = new List<RoutingData>();

        savedMessages.Add(new RoutingData(null, DateTime.Now, null, 1, 1, 1));

        savedMessages.Add(new RoutingData(DateTime.Now, DateTime.Now, null, 1, 1, 2));

        savedMessages.Add(new RoutingData(DateTime.Now, DateTime.Now, null, 1, 1, 3));

        incomingMessages.Add(new RoutingData(DateTime.Now, DateTime.Now, null, 1, 1, 1));

        incomingMessages.Add(new RoutingData(null, DateTime.Now, null, 1, 1, 2));

        incomingMessages.Add(new RoutingData(null, DateTime.Now, null, 1, 1, 3));

        incomingMessages.Add(new RoutingData(DateTime.Now, DateTime.Now, null, 1, 1, 4));

        incomingMessages.Add(new RoutingData(DateTime.Now, DateTime.Now, null, 1, 1, 5));

        List<RoutingData> updatedMessages = new List<RoutingData>();

        updatedMessages.Concat(incomingMessages.Where(incomingMessage => !savedMessages.Any(savedMessage => (incomingMessage.Reference == savedMessage.Reference))));

        savedMessages.ForEach(savedMessage => {

            incomingMessages.Where(incoming => incoming.Reference == savedMessage.Reference).ToList().ForEach((incomingMessage) => {

                if (savedMessage.FirstReceived == null && incomingMessage.FirstReceived != null) {

                    Console.WriteLine("FirstReceived is null from: " + savedMessage.Reference);

                    savedMessage.FirstReceived = incomingMessage.FirstReceived;

                    updatedMessages.Add(incomingMessage);

                }

                else {

                    Console.WriteLine("FirstReceived is not null from: " + savedMessage.Reference);

                    updatedMessages.Add(savedMessage);  

                }

            });

        });

        updatedMessages.ForEach(message => {Console.WriteLine(message.FirstReceived.ToString());});

        Console.WriteLine(updatedMessages.Count);

    }

    public class RoutingData {

        public DateTime? FirstReceived { get; set; }

        public DateTime? ProcessedInternally { get; set; }

        public DateTime? SentToOperator { get; set; }

        public int RouteID { get; set; }

        public int SmscAccountID { get; set; }

        public int? Reference { get; set; }

        public int StatusCode { get; set; }

        public RoutingData(DateTime? firstReceived, DateTime? processedInternally, DateTime? sentToOperator, int smslRoute, int smscAccountId, int reference)

        {

            FirstReceived = firstReceived;

            ProcessedInternally = processedInternally;

            SentToOperator = sentToOperator;

            RouteID = smslRoute;

            SmscAccountID = smscAccountId;

            Reference = reference;

        }

}

}