#nullable enable

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text.Json;

​

namespace Test

{

​

    public class DataClass

    {

            public string? LanguageCode { get; set; }

            public DateTime CreationTimestamp { get; set; }

            public string? DBSHEADERPARTSK { get; set; }

            public string? DBSIdentifier { get; set; }

            public int DBSVersion { get; set; }

            public string? Description { get; set; }

            public string? InvoiceNumber { get; set; }

            public Nullable<DateTime> InvoiceTimestamp { get; set; }

            public string? PartNumber { get; set; }

            public string? PartSerialNumber { get; set; }

            public int? PartPerPackage { get; set; }

            public int MfgId { get; set; }

            public int LocationId { get; set; }

    }

​

    public class CounterSale

    {

        public CounterSale()

        {

            this.Part = new List<Part>();

        }

        public string? InvoiceNumber { get; set; }

        public DateTime CreationTimestamp { get; set; }

        public DateTime InvoiceTimestamp { get; set; }

        public List<Part> Part { get; set; }

    }

​

    public class Location

    {

        public Location()

        {

            this.CounterSale = new List<CounterSale>();

        }

        public int LocationID { get; set; }

        public string? DBSIdentifier { get; set; }

        public string? DBSVersion { get; set; }

        public string? InterfaceVersion { get; set; }

        public string? LanguageCode { get; set; }

        public List<CounterSale> CounterSale { get; set; }

    }

​

    public class Part

    {

        public string? PartNumber { get; set; }

        public string? Quantity { get; set; }

        public string? Description { get; set; }

    }

​

    public class Root

    {

        public Root()

        {

            this.Location = new List<Location>();

        }

        public List<Location> Location { get; set; }

    }

​

    class Program

    {

        public static void Main()

        {

            var now = DateTime.Now;

            var result = new List<DataClass> {

                new DataClass{LocationId = 1, DBSIdentifier = "11", InvoiceNumber = "201", CreationTimestamp = now, PartNumber = "301", Description = "A"},

                new DataClass{LocationId = 1, DBSIdentifier = "11", InvoiceNumber = "201", CreationTimestamp = now, PartNumber = "302", Description = "B"},

                new DataClass{LocationId = 1, DBSIdentifier = "11", InvoiceNumber = "202", CreationTimestamp = now, PartNumber = "303", Description = "C"},

                new DataClass{LocationId = 2, DBSIdentifier = "22", InvoiceNumber = "203", CreationTimestamp = now, PartNumber = "301", Description = "A"},

            };

            // Grouping<Key=LocationId, Collection=Grouping<Key={LocationId, InvoiceNumber}, Collection=DataClass>

            var nestedGroups = result

                .GroupBy(dat => new {dat.LocationId, dat.InvoiceNumber})

                .GroupBy(invGroup => invGroup.Key.LocationId)

                //??maybe?? .ToList()

                ;

​

            var root = new Root()

            {

                Location = nestedGroups.Select(locGroup => new Location()

                {

                    LocationID = locGroup.Key,

                    DBSIdentifier = locGroup.First().First().DBSIdentifier,

                    CounterSale = locGroup.Select(invGroup => new CounterSale()

                    {

                        InvoiceNumber = invGroup.Key.InvoiceNumber,

                        CreationTimestamp = invGroup.First().CreationTimestamp,

                        Part = invGroup.Select(dat => new Part()

                        {

                            PartNumber = dat.PartNumber,

                            Description = dat.Description,

                        }).ToList()

                    }).ToList()

                }).ToList()

            };;

​

            var options = new JsonSerializerOptions{ WriteIndented = true };

            string strJson = JsonSerializer.Serialize(root, options);

            Console.WriteLine(strJson);

        }

    }

}

​