Newtonsoft JSON.NET解析为自定义键/值对对象的数组 [英] Newtonsoft JSON.NET parse to array of custom key/value pair objects

问题描述

我在解析给定的JSON数据时遇到了一个奇怪的问题.我有这个JSON结构:

I have this strange issue with parsing given JSON data. I have this JSON structure:

{"value":[
  {"street":"Karlova 25"},
  {"city":"Prague"},
  {"gpsLat":"50.1571"},
  {"gpsLon":"15.0482"}
]}

如何使用Newtonsoft JSON.NET库解析此结构?我尝试使用自己的JsonConverter类:

How to parse this structure using Newtonsoft JSON.NET library? I tried to use my own JsonConverter class:

public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer){
  JArray jarray = (JArray)((JTokenReader)reader).CurrentToken;
  List<AddressValue> values = new List<AddressValue>();
  foreach (var jobj in jarray.Children<JObject>()){
    foreach (JProperty prop in jobj.Properties()){
      values.Add(new AddressValue() { Label = prop.Name, Value = prop.Value.ToString() });
    }
  }
  return values.ToArray();
}

class AddressValue{
  public string Label { get; set; }
  public string Value { get; set; }
}

但是我有一个例外:

Exception thrown: 'Newtonsoft.Json.JsonSerializationException' in Newtonsoft.Json.DLL

Additional information: Unexpected token when deserializing object: StartObject. Path 'value[0]'.

我也试图将其保存到Dictionary:

I also tried to save this to Dictionary:

 [JsonProperty(PropertyName = "value")]
 public Dictionary<string, string> Value{get; set;}

但是我还有另一个例外:

But I have another exception:

$exception  {"Cannot deserialize the current JSON array (e.g. [1,2,3]) into type 'System.Collections.Generic.Dictionary`2[System.String,System.String]' because the type requires a JSON object (e.g. {\"name\":\"value\"}) to deserialize correctly.\r\nTo fix this error either change the JSON to a JSON object (e.g. {\"name\":\"value\"}) or change the deserialized type to an array or a type that implements a collection interface (e.g. ICollection, IList) like List<T> that can be deserialized from a JSON array. JsonArrayAttribute can also be added to the type to force it to deserialize from a JSON array.\r\nPath 'param.value'."}

我做错了什么?谢谢您的回答.

What I am doing wrong? Thank you for your answers.

推荐答案

您似乎想要在JSON中将Dictionary<string, string>表示为对象数组，其中每个嵌套对象都有一个来自字典的键和值.您可以使用以下转换器进行此操作:

It appears that you want to represent a Dictionary<string, string> in your JSON as an array of objects, where each nested object has one key and value from the dictionary. You can do it with the following converter:

public class DictionaryToDictionaryListConverter<TKey, TValue> : JsonConverter 
{
    class DictionaryDTO : Dictionary<TKey, TValue>
    {
        public DictionaryDTO(KeyValuePair<TKey, TValue> pair) : base(1) { Add(pair.Key, pair.Value); }
    }

    public override bool CanConvert(Type objectType)
    {
        return typeof(IDictionary<TKey, TValue>).IsAssignableFrom(objectType) && objectType != typeof(DictionaryDTO);
    }

    public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
    {
        if (reader.TokenType == JsonToken.Null)
            return null;
        var token = JToken.Load(reader);
        var dict = (IDictionary<TKey, TValue>)(existingValue as IDictionary<TKey, TValue> ?? serializer.ContractResolver.ResolveContract(objectType).DefaultCreator());
        if (token.Type == JTokenType.Array)
        {
            foreach (var item in token)
                using (var subReader = item.CreateReader())
                    serializer.Populate(subReader, dict);
        }
        else if (token.Type == JTokenType.Object)
        {
            using (var subReader = token.CreateReader())
                serializer.Populate(subReader, dict);

        }
        return dict;
    }

    public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)
    {
        var dict = (IDictionary<TKey, TValue>)value;
        // Prevent infinite recursion of converters by using DictionaryDTO
        serializer.Serialize(writer, dict.Select(p => new DictionaryDTO(p)));
    }
}

然后按如下所示在您的容器类中使用它:

Then use it in your container class as follows:

public class RootObject
{
    [JsonProperty("value")]
    [JsonConverter(typeof(DictionaryToDictionaryListConverter<string, string>))]
    public Dictionary<string, string> Value { get; set; }
}

请注意，如果键不是唯一的，转换器将在读取过程中引发异常.

Note that the converter will throw an exception during reading if the keys are not unique.

更新

对于AddressValue，您可以使用以下转换器:

For AddressValue you could use the following converter:

public class AddressValueConverter : JsonConverter
{
    public override bool CanConvert(Type objectType)
    {
        return objectType == typeof(AddressValue);
    }

    public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
    {
        if (reader.TokenType == JsonToken.Null)
            return null;
        var addressValue = (existingValue as AddressValue ?? new AddressValue());
        var token = JObject.Load(reader);
        var property = token.Properties().SingleOrDefault();
        if (property != null)
        {
            addressValue.Label = property.Name;
            addressValue.Value = (string)property.Value;
        }
        return addressValue;
    }

    public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)
    {
        var addressValue = (AddressValue)value;
        serializer.Serialize(writer, new Dictionary<string, string> { { addressValue.Label, addressValue.Value } });
    }
}

然后按如下所示使用它:

Then use it as follows:

[JsonConverter(typeof(AddressValueConverter))]
public class AddressValue
{
    public string Label { get; set; }
    public string Value { get; set; }
}

public class RootObject
{
    [JsonProperty("value")]
    public List<AddressValue> Value { get; set; }
}

在两个选项中都进行小提琴演奏此处.

Demo fiddle with both options here.

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