自定义JsonConverter不会调用ReadJson

Question

我为字典编写了一个转换器。我的想法是将其序列化为键和值列表，因此我可以为字典键编写转换器。但由于某些原因ReadJson未调用DictionaryConverterReader。有谁知道为什么？

public class DictionaryConverterWriter : JsonConverter
{
    public override bool CanRead
    {
        get { return false; }
    }

    public override bool CanConvert(Type objectType)
    {
        return typeof(IDictionary).IsAssignableFrom(objectType);
    }

    public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
    {
        throw new NotSupportedException();
    }

    // Convert from Dictionary to a list of keys and values
    public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)
    {
        if (value == null)
        {
            serializer.Serialize(writer, null);
            return;
        }
        else
        {
            var dictionary = (IDictionary)value;
            serializer.Serialize(writer, new DictionaryWrapper(dictionary));
        }
    }
}

public class DictionaryConverterReader : JsonConverter
{
    public override bool CanWrite
    {
        get { return false; }
    }

    public override bool CanConvert(Type objectType)
    {
        Debug.Log(objectType.ToString());
        return objectType == typeof(DictionaryWrapper);
    }

    public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
    {
        Debug.Log("Read");
        var wrapper = serializer.Deserialize<DictionaryWrapper>(reader);
        return wrapper.Unbox();
    }

    public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)
    {
        throw new NotSupportedException();
    }
}

[Serializable]
public class DictionaryWrapper
{
    public IList keys, values;
    public string type;
    public string assembly;

    [JsonConstructor]
    private DictionaryWrapper(IList keys, IList values, string type, string assembly)
    {
        this.keys = keys;
        this.values = values;
        this.type = type;
        this.assembly = assembly;
    }

    public DictionaryWrapper(IDictionary dictionary)
    {
        keys = Extra.ToList(dictionary.Keys);
        values = Extra.ToList(dictionary.Values);
        assembly = dictionary.GetType().Assembly.ToString();
        type = dictionary.GetType().ToString();
    }

    public IDictionary Unbox()
    {
        var dictionary = (IDictionary)Activator.CreateInstance(assembly, type);
        for (int i = 0; i < keys.Count; i++)
            dictionary[keys[i]] = values[i];
        return dictionary;
    }
}

var writeSettings = new JsonSerializerSettings() 
{ 
    Converters = { new DictionaryConverterWriter() }, 
    TypeNameHandling = TypeNameHandling.All 
};
var serialized = JsonConvert.SerializeObject(new Dictionary<string, int>(), writeSettings);

var readSettings= new JsonSerializerSettings() 
{ 
    Converters = { new DictionaryConverterReader() }, 
    TypeNameHandling = TypeNameHandling.All 
};
Debug.Log(JsonConvert.DeserializeObject(serialized, readSettings)); // <-- Returns DictionaryWrapper