using System;

using Newtonsoft.Json;

using System.Collections.Generic;

using System.Linq;

public class Program

{

    public static void Main()

    {

          List<tmpDataObj> testData = new   List<tmpDataObj>();

         testData.Add(new tmpDataObj("12345","2022/11/01"));

         testData.Add(new tmpDataObj("22441","2022/12/01"));

         testData.Add(new tmpDataObj("22441","2022/11/30"));

         testData.Add(new tmpDataObj("12345","2022/11/01"));

        var workData =( from r in testData

                       group r by new {r.VDNO,r.VDSNAME, DTM= r.DTM.Date.ToString("yyyy/MM") } into G

                      select new {

                                VDNO = G.Key.VDNO,

                                VDSNAME = G.Key.VDSNAME,

                                DTM = G.Key.DTM

​

                        }).ToList();

        Console.WriteLine("Fake Data");

        Console.WriteLine(JsonConvert.SerializeObject(workData, Formatting.Indented));

        Console.WriteLine("".PadRight(99,'='));

        Console.WriteLine("Generate sequence");

        var workDataWithSequence =  workData.Select((data,index)=>new {

                                VDNO = data.VDNO,

                                VDSNAME = data.VDSNAME,

                                DTM = data.DTM,

                                SQENO = $"{DateTime.Now:yyyyMM}{index+1:00}"

​

                        });

        Console.WriteLine(JsonConvert.SerializeObject(workDataWithSequence, Formatting.Indented));

    }

    public class tmpDataObj{

      public tmpDataObj(string VDNO,string DT)

      {

          this.VDNO = VDNO;

          this.VDSNAME = $"{VDNO}_NAME";

          this.DTM = DateTime.Parse(DT);

      }

      public DateTime DTM{get;set;}

      public string VDNO{get;set;}

     public string VDSNAME {get;set;}

    }

}