使用 StringComparer 反序列化 JSON 字典

Question

我正在尝试 serialize/deserialize 字典，问题是我用 StringComparer.OrdinalIgnoreCase 比较器创建了字典。

这是我遇到的问题的代码片段：

var dict = new Dictionary<string, Dictionary<string, string>>(StringComparer.OrdinalIgnoreCase);

dict["x"] = new Dictionary<string, string>();
dict["x"]["y"] = "something";

var serialized = JsonConvert.SerializeObject(dict);

var unSerialized = JsonConvert.DeserializeObject<Dictionary<string, Dictionary<string, string>>>(serialized);

Console.WriteLine((dict.Comparer == unSerialized.Comparer ? "Same" : "Different"));

(.NET Fiddle - Try It)

在控制台打印出以下内容：

Different

显然 JSON 序列化程序不会序列化我在创建字典时设置的比较器，但问题是我无法在事后设置比较器，因为 Dictionary<TKey, TValue>.Comparer 是只读。

我确定它与某些自定义有关 JsonSerializerSetting 但我似乎无法弄清楚如何拦截集合创建和 return 具有不同比较器的字典。

Answer 1

如果将反序列化的结果和要使用的比较器都传递给新字典的构造函数，则可以指定要在字典构造函数中使用的比较器：

var deserialized = JsonConvert
    .DeserializeObject<Dictionary<string, Dictionary<string, string>>>(serialized);

var withComparer = new Dictionary<string, Dictionary<string, string>> (
    deserialized, StringComparer.OrdinalIgnoreCase);

Answer 2

您还可以使用 PopulateObject:

填充现有对象

var dict = new Dictionary<string, Dictionary<string, string>>(StringComparer.OrdinalIgnoreCase);

dict["x"] = new Dictionary<string, string>();
dict["x"]["y"] = "something";

var json = JsonConvert.SerializeObject(dict);


var result =  new Dictionary<string, Dictionary<string, string>>(StringComparer.OrdinalIgnoreCase);
JsonConvert.PopulateObject(json, result);

Console.WriteLine(result["x"]["y"]);
Console.WriteLine(result.Comparer == dict.Comparer ? "Same" : "Diff");

输出：

something
Same

Answer 3

可能有点晚了，但可以使用 JsonConverter 扩展生成的 JSON 会更复杂一些，但更灵活。我已经为所描述的案例创建了一个样本，它还不完整
.NET Fiddle - Try It
（如果您决定使用它，请随意扩展）：

public class DictConverter<TValue> : JsonConverter
{
    public override bool CanConvert(Type objectType)
    {
        return true;
    }

    public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
    {
        var obj = JToken.ReadFrom(reader);                
        if (objectType == typeof(Dictionary<string, TValue>))
        {
            var comparer = obj.Value<string>("Comparer");
            Dictionary<string, TValue> result;
            if (comparer == "OrdinalIgnoreCase")
            {
                result = new Dictionary<string, TValue>(StringComparer.OrdinalIgnoreCase);
            }
            else
            {
                result = new Dictionary<string, TValue>();
            }
            obj["Comparer"].Parent.Remove();
            serializer.Populate(obj.CreateReader(), result);
            return result;
        }
        return obj.ToObject(objectType);
    }

    public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)
    {
        var obj = JObject.FromObject(value);
        if (value is Dictionary<string, TValue>)
        {
            if((value as Dictionary<string, TValue>).Comparer == StringComparer.OrdinalIgnoreCase)
                obj.Add("Comparer", JToken.FromObject("OrdinalIgnoreCase"));
        }
        obj.WriteTo(writer);

    }
}

和用法

var dict = new Dictionary<string, Dictionary<string, string>>(StringComparer.OrdinalIgnoreCase);

dict["x"] = new Dictionary<string, string>();
dict["x"]["y"] = "something";

var serialized = JsonConvert.SerializeObject(dict, 
    new DictConverter<Dictionary<string,string>>());
var unSerialized = JsonConvert.DeserializeObject<Dictionary<string, Dictionary<string, string>>>
    (serialized, new DictConverter<Dictionary<string, string>>());

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