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 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/74762080/how-to-deserialize-json-which-is-sometimes-a-dictionary-and-sometimes-an-empty-a

​

public class Foo

{

    public int Id { get; set; }

    public Bar Bar { get; set; } = new Bar();

    [JsonConverter(typeof(JsonSingleOrEmptyArrayConverter<Dictionary<string, int>>))]

    public Dictionary<string, int> Details { get; private set; } = new Dictionary<string, int>();

​

    public override string ToString()

    {

        return $"Id: {Id}, Bar: {Bar.A} {Bar.B}, Details count: {Details.Count}";

    }

}

​

public class Bar

{

    public int A { get; set; }

    public int B { get; set; }

}

​

    public class JsonSingleOrEmptyArrayConverter<T> : JsonConverter where T : class

    {

        // From this answer https://stackoverflow.com/a/29450279/3744182 by https://stackoverflow.com/users/3744182/dbc

        // To https://stackoverflow.com/questions/29449641/deserialize-json-when-a-value-can-be-an-object-or-an-empty-array

        public override bool CanConvert(Type objectType)

        {

            return typeof(T).IsAssignableFrom(objectType);

        }

​

        public override bool CanWrite { get { return false; } }

​

        public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)

        {

            var contract = serializer.ContractResolver.ResolveContract(objectType);

            if (!(contract is Newtonsoft.Json.Serialization.JsonObjectContract || contract is Newtonsoft.Json.Serialization.JsonDictionaryContract))

            {

                throw new JsonSerializationException(string.Format("Unsupported objectType {0} at {1}.", objectType, reader.Path));

            }

​

            switch (reader.SkipComments().TokenType)

            {

                case JsonToken.StartArray:

                    {

                        int count = 0;

                        while (reader.Read())

                        {

                            switch (reader.TokenType)

                            {

                                case JsonToken.Comment:

                                    break;

                                case JsonToken.EndArray:

                                    return existingValue;

                                default:

                                    {

                                        count++;

                                        if (count > 1)

                                            throw new JsonSerializationException(string.Format("Too many objects at path {0}.", reader.Path));

                                        existingValue = existingValue ?? contract.DefaultCreator();

                                        serializer.Populate(reader, existingValue);

                                    }

                                    break;

                            }

                        }

                        // Should not come here.

                        throw new JsonSerializationException(string.Format("Unclosed array at path {0}.", reader.Path));

                    }

​

                case JsonToken.Null:

                    return null;

​

                case JsonToken.StartObject:

                    existingValue = existingValue ?? contract.DefaultCreator();

                    serializer.Populate(reader, existingValue);

                    return existingValue;

​

                default:

                    throw new InvalidOperationException("Unexpected token type " + reader.TokenType.ToString());

            }

        }

​

        public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)

        {

            throw new NotImplementedException();

        }

    }

​

    public static partial class JsonExtensions

    {

        public static JsonReader SkipComments(this JsonReader reader)

        {

            while (reader.TokenType == JsonToken.Comment && reader.Read())

                ;

            return reader;

        }

    }

    class TestClass

    {

        public static void Test()

        {

            var goodJson = @"

{

    'id': 1,

    'details': {

        'apple': 1,

        'tomato': 4,

        'lettuce': 3,

        'onion': 2

    },

    'bar': { 'A': 5, 'B': 6 }

}";

​

            var badJson = @"

{

    'id': 2,

    'details': [],

    'bar': { 'A': 7, 'B': 8 }

}";

​

            var foo1 = JsonConvert.DeserializeObject<Foo>(goodJson);

            Console.WriteLine($"goodJson: {foo1}");

            Assert.AreEqual(4, foo1.Details.Count);

            var foo2 = JsonConvert.DeserializeObject<Foo>(badJson); // JsonSerializationException

            Console.WriteLine($"badJson: {foo2}");

            Assert.AreEqual(0, foo2.Details.Count);

​

        }   

    }

​

​

    public class Program

    {

        public static void Main()

        {

            Console.WriteLine("Environment version: {0} ({1}), {2}", System.Runtime.InteropServices.RuntimeInformation.FrameworkDescription , Environment.Version, Environment.OSVersion);

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

            Console.WriteLine();

​

            try

            {

                TestClass.Test();

            }

            catch (Exception ex)

            {

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

                Console.WriteLine(ex);

                throw;

            }

        }

    }

​