将字典键从json反序列化到.net中的枚举

Question

我正在从API中读取json响应,其中包含有关图像的信息.
它是这样的字典格式:

images: {
    low_resolution: {
        url: "...",
        width: 150,
        height: 150
    },
    high_resolution: {
        url: "...",
        width: 450,
        height: 450
    }
}

我将响应反序列化为对象,并将图像转换为Dictionary属性,如下所示:

[DataContract()]
public class Post
{
    ...
    [DataMember(Name = "images")]
    public IDictionary<string, Media> Images { get; set; }
    ...
}

HttpResponseMessage response = await client.GetAsync(query);
if (response.IsSuccessStatusCode)
{
    post = await response.Content.ReadAsAsync<Post>();
}

到目前为止,这一切都很好,但我宁愿将图像分辨率信息反序列化为枚举值.
所以我创建了一个枚举ImageResolution并将字典键更改string为ImageResolution.

这也成功反序列化,只要实际的枚举值等于json字符串,但我想更改枚举值.
根据其他各种帖子,我尝试了以下内容:

[DataContract()]
public enum ImageResolution
{
    [EnumMember(Value = "low_resolution")]
    Low,

    [EnumMember(Value = "high_resolution")]
    High,
}

从搜索我也尝试添加:

[JsonConverter(typeof(StringEnumConverter))]

但迄今为止没有任何工作.
响应中有另一个属性,我成功反序列化为枚举并使用JsonConverter属性更改枚举值,但这是一个直接的属性而不是字典键,所以我猜测它是一个字典键导致一些的问题.

是否可以将json值反序列化为不同文本值的枚举字典键？

Answer 1

您需要指示写CustomConverter整个字典这里.

我修改了代码以使用EnumMember而不是其他帖子中使用的前缀:

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(ToEnum<ImageResolution>(pair.Key.ToString()), pair.Value);

        return finalDictionary;
    }

    private T ToEnum<T>(string str)
    {
        var enumType = typeof(T);
        foreach (var name in Enum.GetNames(enumType))
        {
            var enumMemberAttribute = ((EnumMemberAttribute[])enumType.GetField(name).GetCustomAttributes(typeof(EnumMemberAttribute), true)).Single();
            if (enumMemberAttribute.Value == str) return (T)Enum.Parse(enumType, name);
        }
        return default(T);
    }

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

并在词典中使用它:

 [DataContract]
 public class Post
 {
    [JsonConverter(typeof(DictionaryWithSpecialEnumKeyConverter))]
    [DataMember(Name = "images")]
    public Dictionary<ImageResolution, Media> Images { get; set; }
 }