using System;

using System.Collections;

using System.Collections.Generic;

using System.Linq;

using System.Text;

using System.Runtime.Serialization.Formatters;

using System.IO;

using System.Data;

using System.ComponentModel.DataAnnotations;

using System.Globalization;

using System.Reflection;

using System.Collections.ObjectModel;

​

using Newtonsoft.Json;

using Newtonsoft.Json.Linq;

using Newtonsoft.Json.Converters;

using Newtonsoft.Json.Serialization;    

​

using NUnit.Framework; // Throws NUnit.Framework.AssertionException

​

//https://stackoverflow.com/questions/66268617/c-sharp-newtonsoft-single-object-or-array-jsonconverter-not-working-no-errors

​

public class DummyDataModel

{

    public List<SomeFile> someFile { get; } = new List<SomeFile>();

    public partial class SomeFile

    {

        public string name { get; set; } = "";

​

        [JsonConverter(typeof(SingleObjectOrArrayJsonConverter<SomeA>))]

        public List<SomeA> a { get; } = new List<SomeA>();

        //public SomeA a { get; set; } = new SomeA();

    }

​

    public partial class SomeA

    {

        public string asub { get; set; } = "";

        public string atracking { get; set; } = "";

        public string adate { get; set; } = "";

    }

​

    internal class SingleObjectOrArrayJsonConverter<T> : JsonConverter<List<T>> where T : class, new()

    {

        public override void WriteJson(JsonWriter writer, List<T> value, JsonSerializer serializer) =>

            // avoid possibility of infinite recursion by wrapping the List<T> with AsReadOnly()

            serializer.Serialize(writer, value.Count == 1 ? (object)value.Single() : value.AsReadOnly());

​

        public override List<T> ReadJson(JsonReader reader, Type objectType, List<T> existingValue, bool hasExistingValue, JsonSerializer serializer)

        {

            existingValue ??= new ();

            switch (reader.TokenType)

            {

                case JsonToken.StartObject: existingValue.Add(serializer.Deserialize<T>(reader)); break;

                case JsonToken.StartArray: serializer.Populate(reader, existingValue); break;

                default: throw new ArgumentOutOfRangeException($"Converter does not support JSON token type {reader.TokenType}.");

            };

            return existingValue;

        }

    }

}

​

    class TestClass

    {

        public static void Test()

        {

            var unitJSON = GetJson();

            DummyDataModel uTest = JsonConvert.DeserializeObject<DummyDataModel>(unitJSON);

​

            Console.WriteLine( $"Did Test:\n{JsonConvert.SerializeObject(uTest, Formatting.Indented)}" );

        }   

        static string GetJson()

        {

            return @"{

""somefile"": [

    {

        ""name"": ""Bob"",

        ""a"": {

            ""asub"": ""Bob"",

            ""atracking"": ""Bob"",

            ""adate"": "" Bob""

        }

    },

    {

        ""name"": ""Bob"",

        ""a"": [

            {

                ""asub"": ""Bob"",

                ""atracking"": ""Bob"",

                ""adate"": ""Bob""

            },

            {

                ""asub"": ""Bob"",

                ""atracking"": ""Bob"",

                ""adate"": ""Bob""

            }

        ]

    }

]

}

";

        }

    }

​

    public class Program

    {

        public static void Main()

        {

            Console.WriteLine("Environment version: {0} ({1})", System.Runtime.InteropServices.RuntimeInformation.FrameworkDescription , GetNetCoreVersion());

            Console.WriteLine("{0} version: {1}", typeof(JsonSerializer).Assembly.GetName().Name,  typeof(JsonSerializer).Assembly.FullName);

            Console.WriteLine();

​

            try

            {

                TestClass.Test();

            }

            catch (Exception ex)

            {

                Console.WriteLine("Failed with unhandled exception: ");

                Console.WriteLine(ex);

                throw;

            }

        }

        public static string GetNetCoreVersion()

        {

            //https://techblog.dorogin.com/how-to-detect-net-core-version-in-runtime-ecd65ad695be

            //

            var assembly = typeof(System.Runtime.GCSettings).GetTypeInfo().Assembly;

            var assemblyPath = assembly.Location.Split(new[] { '/', '\\' }, StringSplitOptions.RemoveEmptyEntries);

            int netCoreAppIndex = Array.IndexOf(assemblyPath, "Microsoft.NETCore.App");

            if (netCoreAppIndex > 0 && netCoreAppIndex < assemblyPath.Length - 2)

                return assemblyPath[netCoreAppIndex + 1];

            return null;

        }

    }

​