How to use class fields with System.Text.Json.JsonSerializer?

Question

I recently upgraded a solution to be all .NET Core 3 and I have a class that requires the class variables to be fields. This is a problem since the new System.Text.Jso

Answer 1

Fields now work in the prerelease version (I tried 5.0.0-rc.1.20451.14), but you have to enable the option (details in #34558 and #876):

// System.Text.Json 5.0.0-rc.1.20451.14
// using System.Text.Json;

static void Main()
{
    var car = new Car { Model = "Fit", Year = 2008 };

    // Enable support
    var options = new JsonSerializerOptions { IncludeFields = true };

    // Pass "options"
    var json = JsonSerializer.Serialize(car, options);

    // Pass "options"
    var carDeserialized = JsonSerializer.Deserialize<Car>(json, options);

    Console.WriteLine(carDeserialized.Model); // Writes "Fit"
}

public class Car
{
    public int Year { get; set; }
    public string Model;
}

Answer 2

Please try this library I wrote as an extension to System.Text.Json to offer missing features: https://github.com/dahomey-technologies/Dahomey.Json.

You will find support for fields.

using System.Text.Json;
using Dahomey.Json

public class Car
{
    public int Year { get; set; } // does serialize correctly
    public string Model; // will serialize correctly
}

static void Problem() {
    JsonSerializerOptions options = new JsonSerializerOptions();
    options.SetupExtensions(); // extension method to setup Dahomey.Json extensions

    Car car = new Car()
    {
        Model = "Fit",
        Year = 2008,
    };
    string json = JsonSerializer.Serialize(car, options); // {"Year":2008,"Model":"Fit"}
    Car carDeserialized = JsonSerializer.Deserialize<Car>(json);

    Console.WriteLine(carDeserialized.Model); // Fit
}