System.Text.Json 序列/反序列化 abstrac

    public enum SKUTypes
    {
        /// <summary>
        /// 普通，SKU 的价格直接体现在 SKU 中
        /// </summary>
        Normal = 0,

        /// <summary>
        /// 日历类型，SKU 的价格需要从日历价格接口中取
        /// </summary>
        Daily = 1,

        /// <summary>
        /// 需要选择日期的, 比如酒店, 需要选择日期才能查价格
        /// </summary>
        ChoiceDate = 2
    }

    [JsonConverter(typeof(SKUConverter))]
    public abstract class BaseSKU
    {
        /// <summary>
        /// 是否是日历类型的 SKU
        /// </summary>
        public abstract SKUTypes SKUType { get; }
...
...
    public class SKU : BaseSKU
    {
        /// <summary>
        /// 
        /// </summary>
        public override SKUTypes SKUType => SKUTypes.Normal;
...
...
    public class DailySKU : BaseSKU
    {
        /// <summary>
        /// 
        /// </summary>
        public override SKUTypes SKUType => SKUTypes.Daily;
...
...

    public class SKUConverter : JsonConverter<BaseSKU>
    {

        /// <summary>
        /// 
        /// </summary>
        /// <param name="reader"></param>
        /// <param name="typeToConvert"></param>
        /// <param name="options"></param>
        /// <returns></returns>
        public override BaseSKU Read(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
        {
            //reader 是 struct , 如果直接用 reader 的话, 会因为位置已改变, 下面的 Deserializer 报错
            var tmpReader = reader;
            var detect = JsonSerializer.Deserialize<TypeDetectSKU>(ref tmpReader, options);


            return detect.SKUType switch
            {
                SKUTypes.Daily => (BaseSKU)JsonSerializer.Deserialize(ref reader, typeof(DailySKU), options),
                SKUTypes.Normal => (BaseSKU)JsonSerializer.Deserialize(ref reader, typeof(SKU), options),
                SKUTypes.ChoiceDate => (BaseSKU)JsonSerializer.Deserialize(ref reader, typeof(HotelSKU), options),
                _ => throw new NotSupportedException($"SKUType:{detect.SKUType}"),
            };
        }

        /// <summary>
        /// 
        /// </summary>
        /// <param name="writer"></param>
        /// <param name="value"></param>
        /// <param name="options"></param>
        public override void Write(Utf8JsonWriter writer, BaseSKU value, JsonSerializerOptions options)
        {
            JsonSerializer.Serialize(writer, value, value?.GetType() ?? typeof(object), options);
        }



        /// <summary>
        /// 
        /// </summary>
        private class TypeDetectSKU : BaseSKU
        {
            /// <summary>
            /// 
            /// </summary>
            [JsonPropertyName("SKUType")]
            public SKUTypes _SKUType { get; set; }

            /// <summary>
            /// 
            /// </summary>
            [JsonIgnore]
            public override SKUTypes SKUType => this._SKUType;
        }
    }