This program writes a log of JSON report files which logs file entries between the origin directory and a backup directory. If the file does not exist on a backup directory, it is then copied over from the source folder and the json file is marked with a bool state to indicate if the archive file exists.

Program.cs

using Newtonsoft.Json;
using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Runtime.InteropServices;
using System.Threading;

namespace TestConsoleApp
{
    internal static class Program
    {
        internal static void Main(string[] args)
        {
            if (!Directory.Exists(Json_PathBuilder.JsonDir))
                Directory.CreateDirectory(Json_PathBuilder.JsonDir);
            if (!Directory.Exists(Json_PathBuilder.Destination_Path))
                Directory.CreateDirectory(Json_PathBuilder.Destination_Path);
            Thread ProcessFiles_Thread = new Thread(() => Process_Files(Environment.GetFolderPath(Environment.SpecialFolder.Desktop)));
            ProcessFiles_Thread.Name = "Directory_Searcher";
            ProcessFiles_Thread.Start();
        }

        internal static void Process_Files(string in_Directory)
        {
            JSon_Builder.Prep_Json(Directory.GetFiles(in_Directory, "*.*", SearchOption.AllDirectories).ToList(), Json_PathBuilder.Destination_Path);
        }
    }

    public static class JSon_Builder
    {
        private static int File_Incrementer { get; set; }

        public static void Prep_Json(List<string> listOf_Files, string file_Destination)
        {
            foreach (string file in listOf_Files)
            {
                if (File.Exists(file))
                {
                    if (!File.Exists(Path.Combine(Json_PathBuilder.JsonDir, string.Concat(Path.GetFileName(Json_PathBuilder.Json_File).Substring(0, 7), $"_{File_Incrementer}.txt"))))
                        File.Create(Path.Combine(Json_PathBuilder.JsonDir, string.Concat(Path.GetFileName(Json_PathBuilder.Json_File).Substring(0, 7), $"_{File_Incrementer}.txt")));
                    if (File_ToLarge(Path.Combine(Json_PathBuilder.JsonDir, string.Concat(Path.GetFileName(Json_PathBuilder.Json_File).Substring(0, 7), $"_{File_Incrementer}.txt"))))
                    {
                        File_Incrementer++;
                        string jSonFileName = string.Concat(Path.GetFileName(Json_PathBuilder.Json_File).Substring(0, 7), $"_{File_Incrementer}.txt");

                        Write_Json(file, file_Destination, jSonFileName);
                    }
                    else
                    {
                        Write_Json(file, file_Destination, Path.Combine(Json_PathBuilder.JsonDir, string.Concat(Path.GetFileName(Json_PathBuilder.Json_File).Substring(0, 7), $"_{File_Incrementer}.txt")));
                    }
                }
            }
        }

        private static bool File_ToLarge(string current_jSonFile)
        {
            long fileSize = new FileInfo(current_jSonFile).Length;
            int maxSize = 3670016;
            if (fileSize > maxSize)
                return true;
            else
                return false;
        }

        private static void Write_Json(string file, string file_Destination, string toJson_File)
        {
            new JsonSerializer().Formatting = Formatting.Indented;
            bool exists = File.Exists(Path.Combine(file_Destination, Path.GetFileName(file)));
            if (!exists)
            {
                Thread fileCopy_Thread = new Thread(() => FileCopy_Now(file, Path.Combine(file_Destination, Path.GetFileName(file))));
                fileCopy_Thread.Name = "FileCopy Process"; fileCopy_Thread.Start(); exists = true;
            }
            File.AppendAllText(Path.Combine(Json_PathBuilder.JsonDir, toJson_File), JsonConvert.SerializeObject(new DataStructure(file, Path.Combine(file_Destination, Path.GetFileName(file)), exists), Formatting.Indented));
        }

        private static void FileCopy_Now(string origin, string destination) => File.Copy(origin, destination);
    }

    public class DataStructure
    {
        public DataStructure(string origin, string archive, bool exists_InArchive)
        {
            Origin = origin;
            Archive = archive;
            Exists_InArchive = exists_InArchive;
        }

        public string Origin { get; set; }
        public string Archive { get; set; }
        public bool Exists_InArchive { get; set; }
    }

    public static class Json_PathBuilder
    {
        public static readonly string JsonDir = Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.Desktop), "Json Reports");
        public static readonly string Destination_Path = Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.Desktop), "Backup Files");
        public static readonly string Json_File = Path.Combine(JsonDir, "JsonLog.txt");
    }
}