using System;

using System.Collections;

using System.Collections.Generic;

using System.Linq;

using System.Text;

​

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/78284544/c-sharp-custom-dictionary-with-json-de-serialize/

​

    [JsonConverter(typeof(TypedExtensionDataConverter))]

    public class Root<TKey, TValue> where TValue : DynamicKey where TKey : notnull

    {

        // The fixed properties from the JSON:

        public string id { get; set; }

        public Properties properties { get; set; }

​

        // A dictionary to hold the properties with dynamic names but a fixed structure in the JSON:

        [JsonTypedExtensionData]

        public Dictionary<TKey, TValue> DynamicValues { get; init; } = new();

    }

​

    public class Properties // Properties was not shown in your question

    {

        public string createtime { get; set; }

    }

​

    public abstract class DynamicKey; // DynamicKey was not shown in your question

​

    public class IdAndMetadata : DynamicKey

    {

        public string id { get; set; }

        public Metadata metadata { get; set; }

    }

​

    public class Metadata

    {

        public string metadata0 { get; set; }

        public string metadata1 { get; set; }

    }

​

#nullable enable

​

    [AttributeUsage(AttributeTargets.Field | AttributeTargets.Property, AllowMultiple = false)]

    public sealed class JsonTypedExtensionDataAttribute : Attribute;

​

    public class TypedExtensionDataConverter : JsonConverter

    {

        // TypedExtensionDataConverter taken from this answer https://stackoverflow.com/a/40094403/3744182

        // to https://stackoverflow.com/questions/40088941/how-to-deserialize-a-child-object-with-dynamic-numeric-key-names

        // and adjusted so it can be applied to a class with a generic parameter.

​

        public override bool CanConvert(Type objectType) => throw new NotImplementedException(); // CanConvert() is not called when the converter is applied via attributes

​

        static JsonProperty GetExtensionJsonProperty(JsonObjectContract contract)

        {

            try

            {

                return contract.Properties.Where(p => p.PropertyName != null && p.AttributeProvider?.GetAttributes(typeof(JsonTypedExtensionDataAttribute), false).Any() == true).Single();

            }

            catch (InvalidOperationException ex)

            {

                throw new JsonSerializationException(string.Format("Exactly one property with JsonTypedExtensionDataAttribute is required for type {0}", contract.UnderlyingType), ex);

            }

        }

​

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

        {

            if (!(serializer.ContractResolver.ResolveContract(objectType) is JsonObjectContract contract))

                throw new JsonSerializationException($"Contract for {objectType} is not a JsonObjectContract");

            if (!(contract.DefaultCreator is {} creator))

                throw new JsonSerializationException($"No default creator found for {objectType}");

            var extensionJsonProperty = GetExtensionJsonProperty(contract);

​

            if (reader.MoveToContentAndAssert().TokenType == JsonToken.Null)

                return null;

​

            var jObj = JObject.Load(reader);

​

            var extensionJProperty = (JProperty?)null;

            for (int i = jObj.Count - 1; i >= 0; i--)

            {

                var property = (JProperty)jObj.AsList()[i];

                if (contract.Properties.GetClosestMatchProperty(property.Name) == null)

                {

                    if (extensionJProperty == null)

                    {

                        extensionJProperty = new JProperty(extensionJsonProperty.PropertyName!, new JObject());

                        jObj.Add(extensionJProperty);

                    }

                    ((JObject)extensionJProperty.Value).Add(property.RemoveFromLowestPossibleParent());

                }

            }

​

            var value = existingValue ?? creator();

            using (var subReader = jObj.CreateReader())

                serializer.Populate(subReader, value);

            return value;

        }

​

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

        {

            if (value == null)

            {

                writer.WriteNull();

                return;

            }

            if (!(serializer.ContractResolver.ResolveContract(value.GetType()) is JsonObjectContract contract))

                throw new JsonSerializationException($"Contract for {value.GetType()} is not a JsonObjectContract");

            var extensionJsonProperty = GetExtensionJsonProperty(contract);

​

            JObject jObj;

            using (new PushValue<bool>(true, () => Disabled, (canWrite) => Disabled = canWrite))

            {

                jObj = JObject.FromObject(value!, serializer);

            }

​

            var extensionValue = (jObj[extensionJsonProperty.PropertyName!] as JObject)?.RemoveFromLowestPossibleParent();

            if (extensionValue != null)

                for (int i = extensionValue.Count - 1; i >= 0; i--)

                {

                    var property = (JProperty)extensionValue.AsList()[i];

                    jObj.Add(property.RemoveFromLowestPossibleParent());

                }

​

            jObj.WriteTo(writer);

        }

​

        [ThreadStatic]

        static bool disabled;

​

        // Disables the converter in a thread-safe manner.

        bool Disabled { get { return disabled; } set { disabled = value; } }

​

        public override bool CanWrite => !Disabled;

​

        public override bool CanRead => !Disabled;

    }

​

    public static partial class JsonExtensions

    {

        public static JsonReader MoveToContentAndAssert(this JsonReader reader)

        {

            ArgumentNullException.ThrowIfNull(reader);

            if (reader.TokenType == JsonToken.None)       // Skip past beginning of stream.

                reader.ReadAndAssert();

            while (reader.TokenType == JsonToken.Comment) // Skip past comments.

                reader.ReadAndAssert();

            return reader;

        }

​

        public static JsonReader ReadAndAssert(this JsonReader reader)

        {

            ArgumentNullException.ThrowIfNull(reader);

            if (!reader.Read())

                throw new JsonReaderException("Unexpected end of JSON stream.");

            return reader;

        }

​

        public static TJToken? RemoveFromLowestPossibleParent<TJToken>(this TJToken? node) where TJToken : JToken

        {

            if (node == null)

                return null;

            JToken toRemove;

            var property = node.Parent as JProperty;

            if (property != null)

            {

                // Also detach the node from its immediate containing property -- Remove() does not do this even though it seems like it should

                toRemove = property;

                property.Value = null!;

            }

            else

            {

                toRemove = node;

            }

            if (toRemove.Parent != null)

                toRemove.Remove();

            return node;

        }

        public static IList<JToken> AsList(this IList<JToken> container) => container;

    }

​

    internal struct PushValue<T> : IDisposable

    {

        Action<T> setValue;

        T oldValue;

​

        public PushValue(T value, Func<T> getValue, Action<T> setValue)

        {

            if (getValue == null || setValue == null)

                throw new ArgumentNullException();

            this.setValue = setValue;

            this.oldValue = getValue();

            setValue(value);

        }

​

        // By using a disposable struct we avoid the overhead of allocating and freeing an instance of a finalizable class.

        public void Dispose() => setValue?.Invoke(oldValue);

    }

​

    class TestClass

    {

        public static void Test()

        {

            var json = 

                """

                /* Comment */ {

                    "id": "dataset0",

                    "properties": {

                        "createtime": "datetime format"

                    },

                    "dynamic0": {

                        "id": "123-456",

                        "metadata": {

                            "metadata0": "value0",

                            "metadata1": "value1"

                        }

                    },

                    "dynamic1": {

                        "id": "456-789",

                        "metadata": {

                            "metadata0": "value0"

                        }

                    }

                }

                """;

            var root = JsonConvert.DeserializeObject<Root<string, IdAndMetadata>>(json);

            var settings = new JsonSerializerSettings

            {

                NullValueHandling = NullValueHandling.Ignore,

            };

            var json2 = JsonConvert.SerializeObject(root, Formatting.Indented, settings);

            Console.WriteLine("Deserialized and re-serialized {0}:", root);

            Console.WriteLine(json2);

            Assert.That(JToken.DeepEquals(JsonConvert.DeserializeObject<JToken>(json), JsonConvert.DeserializeObject<JToken>(json2)));

        }   

    }

​

    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;

            }

        }

    }

​