using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

using System.Threading.Tasks;

​

  public class Test

    {

        public Test()

        {

            VariantsRanks = new List<VariantsRank>();

        }

        public int TestId { get; set; }

        public List<VariantsRank> VariantsRanks { get; set; }

    }

​

    public class VariantsRank

    {

        public int VariantId { get; set; }

        public string Name { get; set; }

        public int Rank { get; set; }

​

        public bool Selected { get; set; }

    }

​

​

​

public class Program

{

    public static void Main()

    {

         var List1 = new Test();

            List1.TestId = 100;

            List1.VariantsRanks.Add(new VariantsRank { VariantId = 222, Name = "Cp1", Rank = 0, Selected = false });

            List1.VariantsRanks.Add(new VariantsRank { VariantId = 223, Name = "Cp2", Rank = 1, Selected = false });

            List1.VariantsRanks.Add(new VariantsRank { VariantId = 224, Name = "Cp3", Rank = 2, Selected = false });

            List1.VariantsRanks.Add(new VariantsRank { VariantId = 225, Name = "Cp4", Rank = 3, Selected = false });

            List1.VariantsRanks.Add(new VariantsRank { VariantId = 226, Name = "Cp5", Rank = 4, Selected = false });

​

            var List2 = new Test();

            List2.TestId = 100;

            List2.VariantsRanks.Add(new VariantsRank { VariantId = 223, Name = "Cp2", Rank = 0, Selected = true });

            List2.VariantsRanks.Add(new VariantsRank { VariantId = 225, Name = "Cp4", Rank = 1, Selected = true });

​

            var matchQueue = new Queue<VariantsRank>(

                                from r2 in List2.VariantsRanks

                                join r1 in List1.VariantsRanks on r2.VariantId equals r1.VariantId

                                orderby r2.Rank

                                select r2);

            var matchSet = new HashSet<int>(matchQueue.Select(r2 => r2.VariantId));

            var result = List1.VariantsRanks

                        .OrderBy(r1 => r1.Rank)

                        .Select(r1 => matchSet.Contains(r1.VariantId) ? matchQueue.Dequeue() : r1)

                        .Concat(List2.VariantsRanks

                        .Where(r2 => !matchSet.Contains(r2.VariantId))

                        .OrderBy(r2 => r2.Rank))

                        .Select((r, i) => new VariantsRank { VariantId = r.VariantId, Name = r.Name, Rank = i })

                        .ToList();

​

​

            foreach (var res in result)

            {

                Console.WriteLine("\t{0} {1} {2}", res.Name, res.Rank, res.Selected);

            }

    }

}