JsonSerializerOptions

C#
builder.RegisterInstance(preConfiguredSerializationOptions).Keyed("Sprite");

public class SpriteDeserializaer([KeyFilter("Sprite")] JsonSerializationOptions options) { }

C#
builder.RegisterInstance(preConfiguredSerializationOptions).Keyed("Sprite");

public class SpriteDeserializaer([KeyFilter("Sprite")] JsonSerializationOptions options) { }

public class WeatherForecast
{
    public string CityName { get; set; }
    public decimal Temperature { get; set; }
}

[AttributeUsage(AttributeTargets.Class)]
public class JsonSerializerOptionsAttribute : Attribute
{
    public bool AllowTrailingCommas { get; set; }
    // magic
}

[Route("api/v1/[controller]")]
[ApiController]
[JsonSerializerOptions(AllowTrailingCommas = true)] // <-- custom attribute applied to class but also designed to be able to be applied on methods too
public class LegacyController : ControllerBase
{
    [Route("get")]
    public ActionResult<WeatherForecast> HttpGetAttribute()
    {
        return Ok(new WeatherForecast());
        // returns { cityName = "", temperature = 32.5, }
    }
}

[Route("api/[controller]")]
[ApiController]
public class NewController : ControllerBase
{
    [Route("get")]
    public ActionResult<WeatherForecast> HttpGetAttribute()
    {
        return Ok(new WeatherForecast());
        // returns { cityName = "", temperature = 32.5 }
    }
}

public class WeatherForecast
{
    public string CityName { get; set; }
    public decimal Temperature { get; set; }
}

[AttributeUsage(AttributeTargets.Class)]
public class JsonSerializerOptionsAttribute : Attribute
{
    public bool AllowTrailingCommas { get; set; }
    // magic
}

[Route("api/v1/[controller]")]
[ApiController]
[JsonSerializerOptions(AllowTrailingCommas = true)] // <-- custom attribute applied to class but also designed to be able to be applied on methods too
public class LegacyController : ControllerBase
{
    [Route("get")]
    public ActionResult<WeatherForecast> HttpGetAttribute()
    {
        return Ok(new WeatherForecast());
        // returns { cityName = "", temperature = 32.5, }
    }
}

[Route("api/[controller]")]
[ApiController]
public class NewController : ControllerBase
{
    [Route("get")]
    public ActionResult<WeatherForecast> HttpGetAttribute()
    {
        return Ok(new WeatherForecast());
        // returns { cityName = "", temperature = 32.5 }
    }
}

C#
public class LegacyController([KeyFilter("LegacyOptions") JsonSerializerOptions options)

public class NewController([KeyFilter("NewOptions"] JsonSerializerOptions options)

C#
public class LegacyController([KeyFilter("LegacyOptions") JsonSerializerOptions options)

public class NewController([KeyFilter("NewOptions"] JsonSerializerOptions options)

C#
public class LegacyControlerJsonConverter : JsonConverter<LegacyController> {
  public override DateTimeOffset Read(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options) {
  options.AllowTrailingCommas = true;
  // I *think* this method and a matching read one exist.
  reader.Deserialize<LegacyController>(options);
}

  public override void Write(Utf8JsonWriter writer, LegacyController controller, JsonSerializerOptions options) {
  options.AllowTrailingCommas = true;
  // I *think* this method and a matching read one exist.
  writer.Serialize<LegacyController>(options);
}

C#
public class LegacyControlerJsonConverter : JsonConverter<LegacyController> {
  public override DateTimeOffset Read(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options) {
  options.AllowTrailingCommas = true;
  // I *think* this method and a matching read one exist.
  reader.Deserialize<LegacyController>(options);
}

  public override void Write(Utf8JsonWriter writer, LegacyController controller, JsonSerializerOptions options) {
  options.AllowTrailingCommas = true;
  // I *think* this method and a matching read one exist.
  writer.Serialize<LegacyController>(options);
}