Use Newtonsoft.Json exporting the data to Json file

Export method:

        /// <summary>
        /// 导出文件
        /// </summary>
        public void Export(List<Dict> dicts, string filepath)
        {
            File.WriteAllText(filepath, JsonConvert.SerializeObject(dicts, Formatting.Indented));
        }

transfer:

            var Coll Mongodb.XXX.GetCollection = <of Dict> ( " dict " );
             String [] = ARR new new  String [] { " Major " , " Industry " , " post_type " };            // professional, business, job category 

            var Data = the await coll.Find (d => arr.Contains (d.dict_type)) ToListAsync () ConfigureAwait (.. false ); 

            // create a folder 
            String path = " d: \\ jsonfile " ;
             IF (!Directory.Exists(path))
            {
                Directory.CreateDirectory(path);
            }

            try
            {
                Export(data.Where(d => d.dict_type == arr[0]).ToList(), $"{path}\\{arr[0]}.json");
                Export(data.Where(d => d.dict_type == arr[1]).ToList(), $"{path}\\{arr[1]}.json");
                Export(data.Where(d => d.dict_type == arr[2]).ToList(), $"{path}\\{arr[2]}.json");
            }
            catch(Exception e)
            {
                Console.WriteLine($"{e.Message}：{e.ToString()}");
            }