c# - 强制将空 JSON 数组转换为字典类型

Question

问题是，json_encode() PHP 中的函数为读取其输出的工具留下了歧义。在 PHP 中，列表和字典都是相同类型的 array .

echo json_encode([]); // []
echo json_encode(["5" => "something"]); // {"5": "something"}

在 JSON.NET 中，我想同时强制 []和 {"5": "something"}转换为 Dictionary<string, string>类型。但是它识别[]作为 Dictionary 的禁止结构并抛出异常。

我能否快速将空的 JSON 数组置为空或强制它们转换为空的字典类型？

最终解决方案

我修改了已接受的答案，使其通用并可重复用于其他类型。

public class DictionaryOrEmptyArrayConverter<T,F> : JsonConverter
{
    public override bool CanWrite { get { return false; } }
    public override bool CanConvert(Type objectType)
    {
        return objectType == typeof(Dictionary<T, F>);
    }
    public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
    {
        switch (reader.TokenType)
        {
            case JsonToken.StartArray:
                reader.Read();
                if (reader.TokenType == JsonToken.EndArray)
                    return new Dictionary<T, F>();
                else
                    throw new JsonSerializationException("Non-empty JSON array does not make a valid Dictionary!");
            case JsonToken.Null:
                return null;
            case JsonToken.StartObject:
                var tw = new System.IO.StringWriter();
                var writer = new JsonTextWriter(tw);
                writer.WriteStartObject();
                int initialDepth = reader.Depth;
                while (reader.Read() && reader.Depth > initialDepth)
                {
                    writer.WriteToken(reader);
                }
                writer.WriteEndObject();
                writer.Flush();
                return JsonConvert.DeserializeObject<Dictionary<T, F>>(tw.ToString());
            default:
                throw new JsonSerializationException("Unexpected token!");
        }
    }

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

您应该将它与您的 JSON 对象一起使用，如下例所示:

public class Company
{
    public string industry_name { get; set; }

    [JsonConverter(typeof(DictionaryOrEmptyArrayConverter<int, Upgrade>))]
    public Dictionary<int, Upgrade> upgrades { get; set; }
}

public class Upgrade
{
    public int level { get; set; }
}

它允许您使用 DeserializeObject 快速将 JSON 字符串转换为对象方法:

var result = JsonConvert.DeserializeObject<Company>(jsonString);

Answer 1

您可以使用自定义 JsonConverter 来完成，尽管我认为这个解决方案还有一些不足之处:

    private class DictionaryConverter : JsonConverter
    {
        public override bool CanWrite { get { return false; } }
        public override bool CanConvert(Type objectType)
        {
            return objectType == typeof(Dictionary<string, string>);
        }
        public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
        {
            if (reader.TokenType == JsonToken.StartArray)
            {
                reader.Read();
                if (reader.TokenType == JsonToken.EndArray)
                    return new Dictionary<string, string>();
                else
                    throw new JsonSerializationException("Non-empty JSON array does not make a valid Dictionary!");
            }
            else if (reader.TokenType == JsonToken.Null)
            {
                return null;
            }
            else if (reader.TokenType == JsonToken.StartObject)
            {
                Dictionary<string, string> ret = new Dictionary<string, string>();
                reader.Read();
                while (reader.TokenType != JsonToken.EndObject)
                {
                    if (reader.TokenType != JsonToken.PropertyName)
                        throw new JsonSerializationException("Unexpected token!");
                    string key = (string)reader.Value;
                    reader.Read();
                    if (reader.TokenType != JsonToken.String)
                        throw new JsonSerializationException("Unexpected token!");
                    string value = (string)reader.Value;
                    ret.Add(key, value);
                    reader.Read();
                }
                return ret;
            }
            else
            {
                throw new JsonSerializationException("Unexpected token!");
            }
        }

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

在 https://dotnetfiddle.net/zzlzH4 查看此代码的运行情况