SerializePocos.cs

using System.IO;
using System.Linq;
using System.Text.Json;
using System.Text.Json.Serialization;
using BenchmarkDotNet.Attributes;

namespace MiscBenchmarks
{
    [MemoryDiagnoser]
    public class SerializerMethods
    {
        private MemoryStream _memoryStream;
        private Utf8JsonWriter _jsonWriter;

        private Person _person;

        [GlobalSetup]
        public void Setup()
        {
            _memoryStream = new MemoryStream();
            _jsonWriter = new Utf8JsonWriter(_memoryStream);

            _person = DataGenerator.GetPerson();
        }

        [GlobalCleanup]
        public void Cleanup()
        {
            _memoryStream.Dispose();
            _jsonWriter.Dispose();
        }

        [Benchmark(Baseline = true)]
        public void Serializer()
        {
            JsonSerializer.Serialize(_jsonWriter, _person);

            _memoryStream.SetLength(0);
            _jsonWriter.Reset();
        }

        [Benchmark]
        public void SrcGenSerializer()
        {
            JsonSerializer.Serialize(_jsonWriter, _person, MyJsonContext.Default.Person);
            
            _memoryStream.SetLength(0);
            _jsonWriter.Reset();
        }
    }

    [JsonSerializable(typeof(Person[]))]
    internal partial class MyJsonContext : JsonSerializerContext { }

    internal static class DataGenerator
    {
        private static readonly string[] FirstNames = new[]
        {
            "Steffan", "Garin", "Fahad", "Eliana", "Thea", "Edmund", "Layla", "Tony", "Zakir", "Ariyah"
        };

        private static readonly string[] LastNames = new[]
        {
            "English", "Holder", "Beech", "Simon", "Briggs", "Terry", "Horton", "Leblanc", "Rodriguez", "Atkins"
        };

        public static Person GetPerson() => GetPeople(1)[0];

        public static Person[] GetPeople(int num)
        {
            Random rng = new();

            return Enumerable.Range(1, num).Select(indexer => new Person()
            {
                FirstName = FirstNames[rng.Next(FirstNames.Length)],
                LastName = LastNames[rng.Next(LastNames.Length)]
            }).ToArray();
        }
    }

    internal sealed class Person
    {
        public string FirstName { get; set; }
        public string LastName { get; set; }
    }
}