TargetClass obj1;

// Object to UTF8 byte[]
[Benchmark]
public byte[] Utf8JsonSerializer()
{
    return Utf8Json.JsonSerializer.Serialize(obj1, jsonresolver);
}

// Object to String to UTF8 byte[]
[Benchmark]
public byte[] Jil()
{
    return utf8.GetBytes(global::Jil.JSON.Serialize(obj1));
}

// Object to Stream with StreamWriter
[Benchmark]
public void JilTextWriter()
{
    using (var ms = new MemoryStream())
    using (var sw = new StreamWriter(ms, utf8))
    {
        global::Jil.JSON.Serialize(obj1, sw);
    }
}

// ASP.NET Core, OutputFormatter
public class JsonOutputFormatter : IOutputFormatter //, IApiResponseTypeMetadataProvider
{
    const string ContentType = "application/json";
    static readonly string[] SupportedContentTypes = new[] { ContentType };

    public Task WriteAsync(OutputFormatterWriteContext context)
    {
        context.HttpContext.Response.ContentType = ContentType;

        // Jil, normaly JSON Serializer requires serialize to Stream or byte[].
        using (var writer = new StreamWriter(context.HttpContext.Response.Body))
        {
            Jil.JSON.Serialize(context.Object, writer, _options);
            writer.Flush();
            return Task.CompletedTask;
        }

        // Utf8Json
        // Utf8Json.JsonSerializer.NonGeneric.Serialize(context.ObjectType, context.HttpContext.Response.Body, context.Object, resolver);
    }
}

var p = new Person { Age = 99, Name = "foobar" };

// Object -> byte[] (UTF8)
byte[] result = JsonSerializer.Serialize(p);

// byte[] -> Object
var p2 = JsonSerializer.Deserialize<Person>(result);

// Object -> String
var json = JsonSerializer.ToJsonString(p2);

// Write to Stream
JsonSerializer.Serialize(stream, p2);

// Disassemble generated serializer code.
public sealed class PersonFormatter : IJsonFormatter<Person>
{
    private readonly byte[][] stringByteKeys;
    
    public PersonFormatter()
    {
        // pre-encoded escaped string byte with "{", ":" and ",".
        this.stringByteKeys = new byte[][]
        {
            JsonWriter.GetEncodedPropertyNameWithBeginObject("Age"), // {\"Age\":
            JsonWriter.GetEncodedPropertyNameWithPrefixValueSeparator("Name") // ,\"Name\":
        };
    }

    public sealed Serialize(ref JsonWriter writer, Person person, IJsonFormatterResolver jsonFormatterResolver)
    {
        if (person == null) { writer.WriteNull(); return; }

        // WriteRawX is optimize byte->byte copy when we know src size.
        UnsafeMemory64.WriteRaw7(ref writer, this.stringByteKeys[0]);
        writer.WriteInt32(person.Age); // itoa write directly to avoid ToString + UTF8 encode
        UnsafeMemory64.WriteRaw8(ref writer, this.stringByteKeys[1]);
        writer.WriteString(person.Name);

        writer.WriteEndObject();
    }

    // public unsafe Person Deserialize(ref JsonReader reader, IJsonFormatterResolver jsonFormatterResolver)
}

// Disassemble generated serializer code.
public sealed class PersonFormatter : IJsonFormatter<Person>
{
    // public sealed Serialize(ref JsonWriter writer, Person person, IJsonFormatterResolver jsonFormatterResolver)

    public unsafe Person Deserialize(ref JsonReader reader, IJsonFormatterResolver jsonFormatterResolver)
    {
        if (reader.ReadIsNull()) return null;
        
        reader.ReadIsBeginObjectWithVerify(); // "{"
        
        byte[] bufferUnsafe = reader.GetBufferUnsafe();
        int age;
        string name;
        fixed (byte* ptr2 = &bufferUnsafe[0])
        {
            int num;
            while (!reader.ReadIsEndObjectWithSkipValueSeparator(ref num)) // "}" or ","
            {
                // don't decode string, get raw slice
                ArraySegment<byte> arraySegment = reader.ReadPropertyNameSegmentRaw();
                byte* ptr3 = ptr2 + arraySegment.Offset;
                int count = arraySegment.Count;
                if (count != 0)
                {
                    // match automata per long
                    ulong key = AutomataKeyGen.GetKey(ref ptr3, ref count);
                    if (count == 0)
                    {
                        if (key == 6645569uL)
                        {
                            age = reader.ReadInt32(); // atoi read directly to avoid GetString + int.Parse
                            continue;
                        }
                        if (key == 1701667150uL)
                        {
                            name = reader.ReadString();
                            continue;
                        }
                    }
                }
                reader.ReadNextBlock();
            }
        }

        return new PersonSample
        {
            Age = age,
            Name = name
        };
    }
}

// JsonSerializer.Serialize(new FooBar { FooProperty = 99, BarProperty = "BAR" });
// Result : {"foo":99}
public class FooBar
{
    [DataMember(Name = "foo")]
    public int FooProperty { get; set; }

    [IgnoreDataMember]
    public string BarProperty { get; set; }
}

// default serializer change to allow private/exclude null/snake_case serializer.
JsonSerializer.SetDefaultResolver(StandardResolver.AllowPrivateExcludeNullSnakeCase);

var json = JsonSerializer.ToJsonString(new Person { Age = 23, FirstName = null, LastName = "Foo" });

// {"age":23,"last_name":"Foo"}
Console.WriteLine(json);

public class CustomPoint
{
    public readonly int X;
    public readonly int Y;

    public CustomPoint(int x, int y)
    {
        this.X = x;
        this.Y = y;
    }

    // used this constructor.
    [SerializationConstructor]
    public CustomPoint(int x)
    {
        this.X = x;
    }
}

public class MyPerson
{
    public string Name { get; set; }
    public string[] Addresses { get; set; }

    // ShouldSerialize*membername**
    // method must be `public` and return `bool` and parameter less.
    public bool ShouldSerializeAddresses()
    {
        if (Addresses != null && Addresses.Length != 0)
        {
            return true;
        }
        else
        {
            return false;
        }
    }
}

--

// {"Name":"foo"}
JsonSerializer.ToJsonString(new MyPerson { Name = "foo", Addresses = new string[0] });
        
// {"Name":"bar","Addresses":["tokyo","kyoto"]}
JsonSerializer.ToJsonString(new MyPerson { Name = "bar", Addresses = new[] { "tokyo", "kyoto" } });

// dynamic json deserialize
var json = JsonSerializer.Deserialize<dynamic>(@"{""foo"":""json"",""bar"":100,""nest"":{""foobar"":true}}");

var r1 = json["foo"]; // "json" - dynamic(string)
var r2 = json["bar"]; // 100 - dynamic(double), it can cast to int or other number.
var r3 = json["nest"]["foobar"]; // true

public interface IJsonFormatter<T> : IJsonFormatter
{
    void Serialize(ref JsonWriter writer, T value, IJsonFormatterResolver formatterResolver);
    T Deserialize(ref JsonReader reader, IJsonFormatterResolver formatterResolver);
}

// serialize fileinfo as string fullpath.
public class FileInfoFormatter<T> : IJsonFormatter<FileInfo>
{
    public void Serialize(ref JsonWriter writer, FileInfo value, IJsonFormatterResolver formatterResolver)
    {
        if (value == null) { writer.WriteNull(); return; }

        // if target type is primitive, you can also use writer.Write***.
        formatterResolver.GetFormatterWithVerify<string>().Serialize(ref writer, value.FullName, formatterResolver);
    }

    public FileInfo Deserialize(ref JsonReader reader, IJsonFormatterResolver formatterResolver)
    {
        if (reader.ReadIsNull()) return null;

        // if target type is primitive, you can also use reader.Read***.
        var path = formatterResolver.GetFormatterWithVerify<string>().Deserialize(ref reader, formatterResolver);
        return new FileInfo(path);
    }
}

// JsonReader is struct, always pass ref and do not set local variable.
public List<T> Deserialize(ref JsonReader reader, IJsonFormatterResolver formatterResolver)
{
    // check current state is null. when null, advanced offset. if not, do not.
    if (reader.ReadIsNull()) return null;

    var formatter = formatterResolver.GetFormatterWithVerify<T>();
    var list = new List<T>();

    var count = 0; // managing array-count state in outer(this is count, not index(index is always count - 1)

    // loop helper for Array or Object, you can use ReadIsInArray/ReadIsInObject.
    while (reader.ReadIsInArray(ref count)) // read '[' or ',' when until reached ']'
    {
        list.Add(formatter.Deserialize(ref reader, formatterResolver));
    }

    return list;
}

// JsonWriter is struct, always pass ref and do not set local variable.
public void Serialize(ref JsonWriter writer, List<T> value, IJsonFormatterResolver formatterResolver)
{
    if (value == null) { writer.WriteNull(); return; }

    var formatter = formatterResolver.GetFormatterWithVerify<T>();

    writer.WriteBeginArray(); // "["
    if (value.Count != 0)
    {
        formatter.Serialize(ref writer, value[0], formatterResolver);
    }
    for (int i = 1; i < value.Count; i++)
    {
        writer.WriteValueSeparator(); // write "," manually
        formatter.Serialize(ref writer, value[i], formatterResolver);
    }
    writer.WriteEndArray(); // "]"
}

// use global-singleton CompositeResolver.
// This method initialize CompositeResolver and set to default JsonSerializer
CompositeResolver.RegisterAndSetAsDefault(new IJsonFormatter[] {
    // add custome formatters, use other DateTime format.
    // if target type is struct, requires add nullable formatter too(use NullableXxxFormatter or StaticNullableFormatter(innerFormatter))
    new DateTimeFormatter("yyyy-MM-dd HH:mm:ss"),
    new NullableDateTimeFormatter("yyyy-MM-dd HH:mm:ss")
}, new[] {
    // resolver custom types first
    ImmutableCollectionResolver.Instance,
    EnumResolver.UnderlyingValue,

    // finaly choose standard resolver
    StandardResolver.AllowPrivateExcludeNullSnakeCase
});

// select resolver per invoke.
JsonSerializer.Serialize(value, StandardResolver.Default);
JsonSerializer.Serialize(value, StandardResolver.SnakeCase);
JsonSerializer.Serialize(value, CompositeResolver.Instance);

// create custom composite resolver per project is recommended way.
// let's try to copy and paste:)
public class ProjectDefaultResolver : IJsonFormatterResolver
{
    public static IJsonFormatterResolver Instance = new ProjectDefaultResolver();

    // configure your resolver and formatters.
    static IJsonFormatter[] formatters = new IJsonFormatter[]{
        new DateTimeFormatter("yyyy-MM-dd HH:mm:ss"),
        new NullableDateTimeFormatter("yyyy-MM-dd HH:mm:ss")
    };

    static readonly IJsonFormatterResolver[] resolvers = new[]
    {
        ImmutableCollectionResolver.Instance,
        EnumResolver.UnderlyingValue,
        StandardResolver.AllowPrivateExcludeNullSnakeCase
    };

    ProjectDefaultResolver()
    {
    }

    public IJsonFormatter<T> GetFormatter<T>()
    {
        return FormatterCache<T>.formatter;
    }

    static class FormatterCache<T>
    {
        public static readonly IJsonFormatter<T> formatter;

        static FormatterCache()
        {
            foreach (var item in formatters)
            {
                foreach (var implInterface in item.GetType().GetTypeInfo().ImplementedInterfaces)
                {
                    var ti = implInterface.GetTypeInfo();
                    if (ti.IsGenericType && ti.GenericTypeArguments[0] == typeof(T))
                    {
                        formatter = (IJsonFormatter<T>)item;
                        return;
                    }
                }
            }

            foreach (var item in resolvers)
            {
                var f = item.GetFormatter<T>();
                if (f != null)
                {
                    formatter = f;
                    return;
                }
            }
        }
    }
}

public static MyOwnProjectResolver
{
    // CompositeResolver.Create can create dynamic composite resolver.
    // It can `not` garbage collect and create is slightly high cost.
    // so you should store to static field.
    public static readonly IJsonFormatterResolver Instance = CompositeResolver.Create(
        /* IJsonFormatter[] */,
        /* IJsonFormatterResolver[] */
    );
}

// if serializing, choosed CustomObjectFormatter.
[JsonFormatter(typeof(CustomObjectFormatter))]
public class CustomObject
{
    string internalId;

    public CustomObject()
    {
        this.internalId = Guid.NewGuid().ToString();
    }

    class CustomObjectFormatter : IJsonFormatter<CustomObject>
    {
        public void Serialize(ref JsonWriter writer, CustomObject value, IJsonFormatterResolver formatterResolver)
        {
            formatterResolver.GetFormatterWithVerify<string>().Serialize(ref writer, value.internalId, formatterResolver);
        }

        public CustomObject Deserialize(ref JsonReader reader, IJsonFormatterResolver formatterResolver)
        {
            var id = formatterResolver.GetFormatterWithVerify<string>().Deserialize(ref reader, formatterResolver);
            return new CustomObject { internalId = id };
        }
    }
}

public class Person
{
    public int Age { get; set; }
    public string Name { get; set; }

    [JsonFormatter(typeof(DateTimeFormatter), "yyyy-MM-dd")]
    public DateTime Birth { get; set; }
}

// with `Amazon.Lambda.Core package`
public class Utf8JsonLambdaSerializer : Amazon.Lambda.Core.ILambdaSerializer
{
    // Note: Default AWS Lambda's JSON.NET Serializer uses special resolver for handle below types.
    // Amazon.S3.Util.S3EventNotification+ResponseElementsEntity
    // Amazon.Lambda.KinesisEvents.KinesisEvent+Record
    // Amazon.DynamoDBv2.Model.StreamRecord
    // Amazon.DynamoDBv2.Model.AttributeValue
    // If you want to serialize these types, create there custom formatter and setup custom resolver.

    readonly IJsonFormatterResolver resolver;

    public Utf8JsonLambdaSerializer()
    {
        // if you want to customize other configuration change your own choose resolver directly
        // (Lambda uses default constructor and does not exists configure chance of DefaultResolver)
        this.resolver = JsonSerializer.DefaultResolver;
    }

    public Utf8JsonLambdaSerializer(IJsonFormatterResolver resolver)
    {
        this.resolver = resolver;
    }

    public void Serialize<T>(T response, Stream responseStream)
    {
        Utf8Json.JsonSerializer.Serialize<T>(responseStream, response, resolver);
    }

    public T Deserialize<T>(Stream requestStream)
    {
        return Utf8Json.JsonSerializer.Deserialize<T>(requestStream, resolver);
    }
}

public void ConfigureServices(IServiceCollection services)
{
    services.AddMvc().AddMvcOptions(option =>
    {
        option.OutputFormatters.Clear();
        // can pass IJsonFormatterResolver for customize.
        option.OutputFormatters.Add(new JsonOutputFormatter(StandardResolver.Default));
        option.InputFormatters.Clear();
        // if does not pass, library should use JsonSerializer.DefaultResolver.
        option.InputFormatters.Add(new JsonInputFormatter());
    });
}

byte[] buffer = null; // buffer is automatically ensure.
var offset = 0;
var writeSize = NumberConverter.WriteInt64(ref buffer, offset, 99999);

int readCount;
var value = NumberConverter.ReadInt64(buffer, 0, out readCount);

// Simple usage(directory)
Utf8Json.UniversalCodeGenerator.exe -d "..\src\Shared\Request,..\src\Shared\Response" -o "Utf8JsonGenerated.cs"

// CompositeResolver is singleton helper for use custom resolver.
// Ofcourse you can also make custom resolver.
Utf8Json.Resolvers.CompositeResolver.RegisterAndSetAsDefault(
    // use generated resolver first, and combine many other generated/custom resolvers
    Utf8Json.Resolvers.GeneratedResolver.Instance,

    // set StandardResolver or your use resolver chain
    Utf8Json.Resolvers.StandardResolver.Default,
);