c# - 将 JSON 解析为 C# 对象 - 动态获取属性

Question

(跳到粗体部分以获得一句话 tl;dr :)

我有下面的 JSON 对象。在查看它之前，请注意:

• BTC_AMP 之类的货币对列表永远持续下去，为了举例，我将其截断

• BTC_AMP 似乎是一个包含一些字段的 NAMED OBJECT。

  {
  "BTC_AMP": {
      "asks": [
          [
              "0.00007400",
              5
          ]
      ],
      "bids": [
          [
              "0.00007359",
              163.59313969
          ]
      ],
      "isFrozen": "0",
      "seq": 38044678
  },
  "BTC_ARDR": {
      "asks": [
          [
              "0.00003933",
              7160.61031389
          ]
      ],
      "bids": [
          [
              "0.00003912",
              1091.21852308
          ]
      ],
      "isFrozen": "0",
      "seq": 16804479
  },
  }
  

我可以使用 Json.NET 很好地映射对象如所述here .我的问题是，在我看来，我需要为一千个货币对创建一个对象并预定义属性名称，例如 BTC_AMP、BTC_ARDR 等。

您可能会看到我的目标...如何在不预先创建每一对名称的情况下映射此对象？

希望我在这里遗漏了一些明显的东西。

编辑:代码看起来像这样，我不想做的事:

public class PoloniexPriceVolume
{
    public string Price { get; set; }
    public double Volume { get; set; }
}

public class PoloniexPairInfo
{
    public PoloniexPriceVolume Asks { get; set; }
    public PoloniexPriceVolume Bids { get; set; }
    public bool IsFrozen { get; set; }
    public int Seq { get; set; } 

}

public class PoloniexOrderBook
{
    public PoloniexPairInfo BTC_AMP { get; set; }
    //One thousand and one Arabian currency pairs here
}

---

编辑 2...如果我在某处有一个货币对列表，我至少可以动态创建一个对象/对象的属性吗？似乎没有手写那么可笑。

Answer 1

这里有几个问题:

• 您的根对象具有大量可变数量的属性，其值对应于固定数据类型 PoloniexPairInfo .由于您不想创建对所有这些属性进行硬编码的根类型，因此您可以反序列化为 Dictionary<string, PoloniexPairInfo>如图Create a strongly typed c# object from json object with ID as the name .

• Bid和 Ask属性在 JSON 中表示为不同类型值的数组:

  [
    [
      "0.00007359",
      163.59313969
    ]
  ]
  

  您想将内部数组映射到固定的 POCO PoloniexPriceVolume通过将特定数组索引处的值绑定(bind)到特定的 C# 属性。您可以使用 ObjectToArrayConverter<PoloniexPriceVolume> 执行此操作来自 C# JSON.NET - Deserialize response that uses an unusual data structure .

• 最后，JSON值"isFrozen"有一个字符串值“0”，但您想将其映射到 bool值 public bool IsFrozen { get; set; } .您可以通过调整 BoolConverter 来做到这一点来自 Convert an int to bool with Json.Net .

将所有这些放在一起，您可以使用以下模型和转换器反序列化您的 JSON:

[JsonConverter(typeof(ObjectToArrayConverter<PoloniexPriceVolume>))]
public class PoloniexPriceVolume
{
    [JsonProperty(Order = 1)]
    public string Price { get; set; }
    [JsonProperty(Order = 2)]
    public double Volume { get; set; }
}

public class PoloniexPairInfo
{
    public List<PoloniexPriceVolume> Asks { get; set; }
    public List<PoloniexPriceVolume> Bids { get; set; }
    [JsonConverter(typeof(BoolConverter))]
    public bool IsFrozen { get; set; }
    public int Seq { get; set; }
}

public class ObjectToArrayConverter<T> : JsonConverter
{
    //https://stackoverflow.com/a/39462464/3744182
    public override bool CanConvert(Type objectType)
    {
        return typeof(T) == objectType;
    }

    public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)
    {
        var objectType = value.GetType();
        var contract = serializer.ContractResolver.ResolveContract(objectType) as JsonObjectContract;
        if (contract == null)
            throw new JsonSerializationException(string.Format("invalid type {0}.", objectType.FullName));
        writer.WriteStartArray();
        foreach (var property in SerializableProperties(contract))
        {
            var propertyValue = property.ValueProvider.GetValue(value);
            if (property.Converter != null && property.Converter.CanWrite)
                property.Converter.WriteJson(writer, propertyValue, serializer);
            else
                serializer.Serialize(writer, propertyValue);
        }
        writer.WriteEndArray();
    }

    public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
    {
        var contract = serializer.ContractResolver.ResolveContract(objectType) as JsonObjectContract;
        if (contract == null)
            throw new JsonSerializationException(string.Format("invalid type {0}.", objectType.FullName));

        if (reader.MoveToContentAndAssert().TokenType == JsonToken.Null)
            return null;
        if (reader.TokenType != JsonToken.StartArray)
            throw new JsonSerializationException(string.Format("token {0} was not JsonToken.StartArray", reader.TokenType));

        // Not implemented: JsonObjectContract.CreatorParameters, serialization callbacks, 
        existingValue = existingValue ?? contract.DefaultCreator();

        using (var enumerator = SerializableProperties(contract).GetEnumerator())
        {
            while (true)
            {
                switch (reader.ReadToContentAndAssert().TokenType)
                {
                    case JsonToken.EndArray:
                        return existingValue;

                    default:
                        if (!enumerator.MoveNext())
                        {
                            reader.Skip();
                            break;
                        }
                        var property = enumerator.Current;
                        object propertyValue;
                        // TODO:
                        // https://www.newtonsoft.com/json/help/html/Properties_T_Newtonsoft_Json_Serialization_JsonProperty.htm
                        // JsonProperty.ItemConverter, ItemIsReference, ItemReferenceLoopHandling, ItemTypeNameHandling, DefaultValue, DefaultValueHandling, ReferenceLoopHandling, Required, TypeNameHandling, ...
                        if (property.Converter != null && property.Converter.CanRead)
                            propertyValue = property.Converter.ReadJson(reader, property.PropertyType, property.ValueProvider.GetValue(existingValue), serializer);
                        else
                            propertyValue = serializer.Deserialize(reader, property.PropertyType);
                        property.ValueProvider.SetValue(existingValue, propertyValue);
                        break;
                }
            }
        }
    }

    static IEnumerable<JsonProperty> SerializableProperties(JsonObjectContract contract)
    {
        return contract.Properties.Where(p => !p.Ignored && p.Readable && p.Writable);
    }
}

public static partial class JsonExtensions
{
    //https://stackoverflow.com/a/39462464/3744182
    public static JsonReader ReadToContentAndAssert(this JsonReader reader)
    {
        return 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;
    }
}

public class BoolConverter : JsonConverter
{
    public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)
    {
        writer.WriteValue(((bool)value) ? "1" : "0");
    }

    public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
    {
        if (reader.TokenType == JsonToken.Null)
            return null;

        var token = JToken.Load(reader);

        if (token.Type == JTokenType.Boolean)
            return (bool)token;
        return token.ToString() != "0";
    }

    public override bool CanConvert(Type objectType)
    {
        return objectType == typeof(bool);
    }
}

最后，做:

var orderBook = JsonConvert.DeserializeObject<Dictionary<string, PoloniexPairInfo>>(jsonString);

工作 .Net fiddle .