Program.cs

using System;
using System.Collections.Generic;

namespace JsonReader
{
    class Program
    {
        static void Main(string[] args)
        {
            var data = new List<object>();
            const int len = 300000;
            long sum = 0;
            var rnd = new System.Random();
            for (int i = 0; i < len; ++i)
            {
                var x = rnd.Next();
                sum += x;
                data.Add(new {hoge = x, piyo = "foo"});
            }
            var json = System.Text.Json.JsonSerializer.SerializeToUtf8Bytes(data);

            var sw3 = new System.Diagnostics.Stopwatch();
            var sw4 = new System.Diagnostics.Stopwatch();
            sw3.Start();
            var a = Hurisake.JsonDeserializer.Deserialize(json)!.Value;
            // https://github.com/neuecc/Utf8Json
            // var a = Utf8Json.JsonSerializer.Deserialize<dynamic>(json);
            sw3.Stop();
            sw4.Start();
            long sum2 = 0;
            if (a.Count != len) throw new Exception();
            for (int i = 0; i < a.Count; ++i)
            {
                sum2 += (int)a[i]["hoge"];
            }

            if (sum != sum2) throw new Exception();
            sw4.Stop();
            Console.WriteLine(sw3.ElapsedMilliseconds);
            Console.WriteLine(sw4.ElapsedMilliseconds);
        }
    }
}