using System;

using System.Collections;

using System.Collections.Generic;

using System.Linq;

using System.Text;

​

using System.Text.Json;

using System.Text.Json.Serialization;

using System.Text.Json.Serialization.Metadata;

using System.Text.Json.Nodes;

​

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

​

#nullable enable

​

//https://stackoverflow.com/questions/76444369/how-to-add-a-new-property-to-jsonelement-using-system-text-json

​

    public static class JsonExtensions

    {

        public static JsonNode TryAddPropertyToArrayElements<TProperty>(this JsonNode node, string name, TProperty value)

        {

            if (node is JsonArray array)

                foreach (var obj in array.OfType<JsonObject>())

                    obj[name] = JsonSerializer.SerializeToNode(value);

            return node;

        }

​

        public static JsonElement TryAddPropertyToArrayElements<TProperty>(this JsonElement element, string name, TProperty value) =>

            element.ValueKind == JsonValueKind.Array

            ? JsonSerializer.SerializeToElement(JsonSerializer.Deserialize<JsonNode>(element)!.TryAddPropertyToArrayElements(name, value))

            : element;

​

        public static object? TryAddPropertyToArrayElements<TProperty>(this object? obj, string name, TProperty value) =>

            obj switch

            {

                JsonElement e => e.TryAddPropertyToArrayElements(name, value),

                JsonNode n => n.TryAddPropertyToArrayElements(name, value),

                null => null, // JSON values that are null are deserialized to the c# null value, not some element or node of type null

                _ => throw new ArgumentException("Unexpected type ${obj}"),

            };

    }

​

    class TestClass

    {

        public static void Test()

        {

            var inputOptions = new JsonSerializerOptions

            {

                UnknownTypeHandling = JsonUnknownTypeHandling.JsonNode,

            };

            Console.WriteLine($"Testing with {inputOptions.UnknownTypeHandling}:");

            var json = GetJson();

            var metas = JsonSerializer.Deserialize<Dictionary<string, object?>>(json, inputOptions)!;

            Console.WriteLine($"Type for metas[\"key-1\"] is {metas["key-1"]?.GetType()}");

            metas["key-1"] = metas["key-1"]?

                .TryAddPropertyToArrayElements("newproperty", "test value");

​

            Console.WriteLine($"Type for modified metas[\"key-1\"] is {metas["key-1"]?.GetType()}");

​

            var newJson = JsonSerializer.Serialize(metas, new JsonSerializerOptions { WriteIndented = true });

            Console.WriteLine(newJson);

            Assert.That(newJson.Contains("newproperty") && newJson.Contains("test value"));

            Assert.Throws<ArgumentException>(() => new List<object>().TryAddPropertyToArrayElements("newproperty", "test value"));

            Assert.DoesNotThrow(() => default(object)!.TryAddPropertyToArrayElements("newproperty", "test value"));

        }

        static string GetJson() => 

            """

            {

               "key-2":[],

               "key-1":[

                  {

                     "@name":"SYMBOL",

                     "#text":"005930"

                  },

                  {

                     "@name":"NAME",

                     "#text":"Samsung Electronics"

                  }

               ]

            }

            """;

    }

​

    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("System.Text.Json version: " + typeof(JsonSerializer).Assembly.FullName);

            Console.WriteLine();

​

            try

            {

                TestClass.Test();

            }

            catch (Exception ex)

            {

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

                Console.WriteLine(ex);

                throw;

            }

        }

    }

​