C# JsonSerializer.Serialize 返回一个空对象

我遇到了有关将结构序列化为 JSON 的问题。所以，我有一个结构“坐标”

namespace CoordinatesNameSpace
{
    public struct Coordinates
    {
        public Coordinates(string key, string x, string y, string z)
        {
            this.key = key;
            this.x = x;
            this.y = y;
            this.z = z;
        }
        public string key;
        public string x;
        public string y;
        public string z;
        public override string ToString()
        {
            return $"{key} {this.x} {this.y} {this.z}";
        }
    }
}

所有属性都是公共的，所以我期望 json 序列化器将返回我 { "key": "v", "x": "0.12331212" ... }，但它只返回一个空对象。

using CoordinatesNameSpace;

namespace ObjToJSON
{
    class Program
    {
        static void Main(string[] args)
        {
            List<Coordinates> parsedCoordinatesList = new List<Coordinates>();
            Coordinates _c;
            _c.key = splitted[0]; // "v"
            _c.x = splitted[1]; // "1.324394"
            _c.y = splitted[2]; // "-0.219625"
            _c.z = splitted[3]; // "-0.422554"
            parsedCoordinatesList.Add(_c);

            // returns an [{}, {}, {} ...]
            //string json = JsonSerializer.Serialize<List<Coordinates>>(parsedCoordinatesList);

            // returns {}
            string json = JsonSerializer.Serialize<Coordinates>(parsedCoordinatesList[0]);

有人可以向我解释一下 - 为什么这样做以及如何使其正确序列化吗？

It seems https://github.com/dotnet/runtime/issues/876目前System.Text.Json不支持序列化字段。将字段更改为属性，一切都应该正常：

public struct Coordinates
{
    public Coordinates(string key, string x, string y, string z)
    {
        this.key = key;
        this.x = x;
        this.y = y;
        this.z = z;
    }
    public string key  { get; set; }
    public string x  { get; set; }
    public string y  { get; set; }
    public string z  { get; set; }
    public override string ToString()
    {
        return $"{key} {this.x} {this.y} {this.z}";
    }
}

也来自docs https://learn.microsoft.com/en-us/dotnet/standard/serialization/system-text-json/how-to?pivots=dotnet-core-3-1#deserialization-behavior:

序列化行为：

...

• 目前，字段被排除。

UPD

Since 可以包含 .NET 5 字段 https://learn.microsoft.com/en-us/dotnet/standard/serialization/system-text-json/how-to?pivots=dotnet-5-0#include-fields要么通过JsonSerializerOptions.IncludeFields全局设置或通过JsonIncludeAttribute.

public struct Coordinates
{
    public Coordinates(string key, string x, string y, string z)
    {
        this.key = key;
        this.x = x;
        this.y = y;
        this.z = z;
    }
    [JsonInclude]
    public string key;
    [JsonInclude]
    public string x;
    [JsonInclude]
    public string y;
    [JsonInclude]
    public string z;

    public override string ToString()
    {
        return $"{key} {this.x} {this.y} {this.z}";
    }
}