`JsonSerializer` support for fields

jsonserializerfields.csproj

<Project Sdk="Microsoft.NET.Sdk">

  <PropertyGroup>
    <OutputType>Exe</OutputType>
    <TargetFramework>net5.0</TargetFramework>
    <LangVersion>preview</LangVersion>
  </PropertyGroup>

</Project>

Program.cs

using System;
using System.Text.Json;

var json = "{\"date\":\"2020-09-06T11:31:01.923395-07:00\",\"temperatureC\":-1,\"temperatureF\":31,\"summary\":\"Scorching\"} ";           
var options = new JsonSerializerOptions()
{
    PropertyNameCaseInsensitive = true,
    IncludeFields = true,
    PropertyNamingPolicy = JsonNamingPolicy.CamelCase
};
var forecast = JsonSerializer.Deserialize<Forecast>(json, options);

Console.WriteLine(forecast.Date);
Console.WriteLine(forecast.TemperatureC);
Console.WriteLine(forecast.TemperatureF);
Console.WriteLine(forecast.Summary);

var roundTrippedJson = JsonSerializer.Serialize<Forecast>(forecast, options);

Console.WriteLine(roundTrippedJson);

public class Forecast{
    public DateTime Date;
    public int TemperatureC;
    public int TemperatureF;
    public string Summary;
}

Produces the following output:

rich@thundera jsonserializerfields % dotnet run
9/6/2020 11:31:01 AM
-1
31
Scorching
{"date":"2020-09-06T11:31:01.923395-07:00","temperatureC":-1,"temperatureF":31,"summary":"Scorching"}