using System;

using System.Collections.Generic;

using System.Linq;

​

public class Program

{

    public static void Main()

    {

        var sampleObjects = new[]

        {

            new SampleObject

            {

                MsfId = 100,

                PgId = new List<string> { "abc" },

                DcId = new List<string> { "123" }

            },

            new SampleObject

            {

                MsfId = 100,

                PgId = new List<string> { "def" },

                DcId = new List<string> { "456" }

            },

            new SampleObject

            {

                MsfId = 101,

                PgId = new List<string> { "abc" },

                DcId = new List<string> { "123" }

            }

        };

        var result = sampleObjects

            .GroupBy(

                o => o.MsfId,

                (k, g) => new SampleObject

                    {

                        MsfId = k,

                        PgId = g.SelectMany(p => p.PgId).Distinct().ToList(),

                        DcId = g.SelectMany(p => p.DcId).Distinct().ToList()

                    });

        foreach(var item in result)

        {

            Console.WriteLine("{");

            Console.WriteLine("    MsfId:{0}", item.MsfId);

            Console.WriteLine("    PgId:{0}", string.Join(", ", item.PgId));

            Console.WriteLine("    DcId:{0}", string.Join(", ", item.DcId));

            Console.WriteLine("},");

        }

    }

}

​

public class SampleObject

{

    public int MsfId { get; set; }

    public List<string> PgId { get; set; }

    public List<string> DcId { get; set; }

}