Question

我有一个JSON：

{ 
    "data": { "A": 5, "B": 6 }, 
    "foo": "foo", 
    "bar": "bar" 
}

我需要将数据反序列化为类：

public Dictionary<MyEnum, int> Data { get; set; }
public string Foo { get; set; }
public string Bar { get; set; }

但MyEnum值分别为CodeA和CodeB，而不仅仅是A和B。

我有一个可以处理转换的自定义转换器。但是如何指定JsonConverter与词典键一起使用？

Answer 1

我认为唯一的方法是为整个Dictionary<MyEnum, int>类型或Dictionary<MyEnum, T>创建一个JsonConverter。

字典键不被视为值，不会通过JsonConverters运行。 TypeConverters本来就是一个解决方案，但枚举转换的默认字符串将在它查看TypeConverters之前输入。

所以...我认为不能以任何其他方式完成。

编辑：

没有经过全面测试，但我在我的项目中使用了类似的东西：

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

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

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

        var valueType = objectType.GetGenericArguments()[1];
        var intermediateDictionaryType = typeof(Dictionary<,>).MakeGenericType(typeof(string), valueType);
        var intermediateDictionary = (IDictionary)Activator.CreateInstance(intermediateDictionaryType);
        serializer.Populate(reader, intermediateDictionary);

        var finalDictionary = (IDictionary)Activator.CreateInstance(objectType);
        foreach (DictionaryEntry pair in intermediateDictionary)
            finalDictionary.Add(Enum.Parse(MyEnum, "Code" + pair.Key, false), pair.Value);

        return finalDictionary;
    }

    public override bool CanConvert(Type objectType)
    {
        return objectType.IsA(typeof(IDictionary<,>)) &&
               objectType.GetGenericArguments()[0].IsA<MyEnum>();
    }
}

你需要这个小帮手：

    public static bool IsA(this Type type, Type typeToBe)
    {
        if (!typeToBe.IsGenericTypeDefinition)
            return typeToBe.IsAssignableFrom(type);

        var toCheckTypes = new List<Type> { type };
        if (typeToBe.IsInterface)
            toCheckTypes.AddRange(type.GetInterfaces());

        var basedOn = type;
        while (basedOn.BaseType != null)
        {
            toCheckTypes.Add(basedOn.BaseType);
            basedOn = basedOn.BaseType;
        }

        return toCheckTypes.Any(x => x.IsGenericType && x.GetGenericTypeDefinition() == typeToBe);
    }

希望它适合你。

Answer 2

以下是使用json和Dictionary以及任何类型的键的问题的通用解决方案：

[JsonObject]
public class MyKeyValuePair<TKey, TValue>
{
    public TKey MyKey;

    public TValue MyValue;

    [JsonConstructor]
    public MyKeyValuePair()
    {

    }

    public MyKeyValuePair(TKey t1, TValue t2)
    {
        MyKey = t1;
        MyValue = t2;
    }
}



[JsonObject]
public class MyDictionaty<TKey, TValue>

{
    public ICollection<MyKeyValuePair<TKey, TValue>> Collection;

    [JsonConstructor]
    public MyDictionaty()
    {

    }
    public MyDictionaty(Dictionary<TKey, TValue> refund)
    {
        Collection = BuildMyKeyValuePairCollection(refund);
    }
    internal Dictionary<TKey, TValue> ToDictionary()
    {
        return Collection.ToDictionary(pair => pair.MyKey, pair => pair.MyValue);
    }

    private ICollection<MyKeyValuePair<TKey, TValue>> BuildMyKeyValuePairCollection(Dictionary<TKey, TValue> refund)
    {
        return refund.Select(o => new MyKeyValuePair<TKey, TValue>(o.Key, o.Value)).ToList();
    }
}




[JsonObject]
public class ClassWithDictionary
{
    [JsonProperty]
    private readonly MyDictionary<AnyKey, AnyValue> _myDictionary;

    private Dictionary<AnyKey, AnyValue> _dic;

    [JsonConstructor]
    public ClassWithDictionary()
    {

    }
    public ClassWithDictionary(Dictionary<AnyKey, AnyValue> dic)
    {
        _dic= dic;
        _myDictionary = new MyDictionaty<AnyKey, AnyValue>(dic);
    }

    public Dictionary<AnyKey, AnyValue> GetTheDictionary()
    {
        _dic = _dic??_myDictionary.ToDictionary();
        return _dic;
    }
}

Answer 3

我无法使用任何TypeConverter解决方案，也不想拥有一个JsonConverter来构建一个字符串字典，然后将所有内容复制到一个新字典中，所以我采用了这样的方法：

public sealed class MyEnumKeyDictionary<TValue> : IReadOnlyDictionary<MyEnum, TValue>, IDictionary<string, TValue>
{
    private readonly Dictionary<MyEnum, TValue> actual = new Dictionary<MyEnum, TValue>();

    // implement IReadOnlyDictionary implicitly, passing everything from `actual`

    // implement IDictionary explicitly, passing everything into/from `actual` after doing Enum.Parse/Enum.ToString
}

json.net：为字典键指定转换器

3 个答案: