如何以特定顺序序列化和反序列化具有重复属性名称的 JSON 对象？

Question

我需要创建一个 C# class 来匹配这个 json 并带有这样的确切括号。

{
    "data": {
        "a": "4",
        "b": "2",
        "c": "3",
        "a": "444",
    },
}

System.Collections.Generic.Dictionary<string, string> 做到了，但它不允许使用相同的密钥进行多次输入，所以这样是行不通的。

List<T> 与自定义数据 class、字符串 [2]、元组或 valueTuples 或 KeyValuePair<string, string> 创建不同的 json，其中每个条目都获得“item1”、“ item1" 或不同的括号。

如何反序列化和序列化这个 JSON？这是我必须支持的客户“标准”。

Answer 1

虽然在技术上没有畸形，JSON 具有重复属性名称的对象被最近的 JSON RFC 不推荐，RFC 8259:

An object structure is represented as a pair of curly brackets surrounding zero or more name/value pairs (or members)...

An object whose names are all unique is interoperable in the sense that all software implementations receiving that object will agree on the name-value mappings. When the names within an object are not unique, the behavior of software that receives such an object is unpredictable. Many implementations report the last name/value pair only. Other implementations report an error or fail to parse the object, and some implementations report all of the name/value pairs, including duplicates.

您可能希望向您的客户建议另一种 JSON 格式，例如单个键值对对象的数组。

也就是说，如果您必须序列化和反序列化具有重复属性的对象，Json.NET将不会这样做的框，你将不得不创建一个 custom JsonConverter 来手动完成。由于 JSON 对象的值都是同一类型（这里是字符串），您可以绑定到 List<KeyValuePair<string, string>>.

首先定义如下模型：

public class Model
{
    [JsonConverter(typeof(KeyValueListAsObjectConverter<string>))]
    public List<KeyValuePair<string, string>> data { get; } = new ();
}

以及以下泛型 JsonConverter<List<KeyValuePair<string, TValue>>>：

public class KeyValueListAsObjectConverter<TValue> : JsonConverter<List<KeyValuePair<string, TValue>>>
{
    public override List<KeyValuePair<string, TValue>> ReadJson(JsonReader reader, Type objectType, List<KeyValuePair<string, TValue>> existingValue, bool hasExistingValue, JsonSerializer serializer)
    {
        if (reader.MoveToContentAndAssert().TokenType == JsonToken.Null)
            return null;
        reader.AssertTokenType(JsonToken.StartObject);
        var list = existingValue ?? (List<KeyValuePair<string, TValue>>)serializer.ContractResolver.ResolveContract(objectType).DefaultCreator();
        while (reader.ReadToContentAndAssert().TokenType != JsonToken.EndObject)
        {
            var name = (string)reader.AssertTokenType(JsonToken.PropertyName).Value;
            var value = serializer.Deserialize<TValue>(reader.ReadToContentAndAssert());
            list.Add(new KeyValuePair<string, TValue>(name, value));
        }
        return list;
    }

    public override void WriteJson(JsonWriter writer, List<KeyValuePair<string, TValue>> value, JsonSerializer serializer)
    {
        writer.WriteStartObject();
        foreach (var pair in value)
        {
            writer.WritePropertyName(pair.Key);
            serializer.Serialize(writer, pair.Value);
        }
        writer.WriteEndObject();
    }
}

public static partial class JsonExtensions
{
    public static JsonReader AssertTokenType(this JsonReader reader, JsonToken tokenType) => 
        reader.TokenType == tokenType ? reader : throw new JsonSerializationException(string.Format("Unexpected token {0}, expected {1}", reader.TokenType, tokenType));
    
    public static JsonReader ReadToContentAndAssert(this JsonReader reader) =>
        reader.ReadAndAssert().MoveToContentAndAssert();

    public static JsonReader MoveToContentAndAssert(this JsonReader reader)
    {
        if (reader == null)
            throw new ArgumentNullException();
        if (reader.TokenType == JsonToken.None)       // Skip past beginning of stream.
            reader.ReadAndAssert();
        while (reader.TokenType == JsonToken.Comment) // Skip past comments.
            reader.ReadAndAssert();
        return reader;
    }

    public static JsonReader ReadAndAssert(this JsonReader reader)
    {
        if (reader == null)
            throw new ArgumentNullException();
        if (!reader.Read())
            throw new JsonReaderException("Unexpected end of JSON stream.");
        return reader;
    }
}

您将能够反序列化和重新序列化问题中显示的 JSON。

演示 fiddle here.

如何以特定顺序序列化和反序列化具有重复属性名称的 JSON 对象？

How to serialize and deserialize a JSON object with duplicate property names in a specific order?

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如何以特定顺序序列化和反序列化具有重复 属性 名称的 JSON 对象？

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如何以特定顺序序列化和反序列化具有重复属性名称的 JSON 对象？