在字典与JSON.Net复杂类型的具体使用序列化 [英] Usage-specific serialization for complex type in Dictionary with JSON.Net

问题描述

我有一个类

public class MyValue 
{
    public String Prop1 { get; set; }
    public String Prop2 { get; set; }
}

这我都用一个类型为普通财产以及字典键。

which I am both using as a type for a normal Property as well as a Dictionary key.

我需要的是一种方式，这样，当这个类被用作属性，它是序列化为

What I need is a way so that when this class is used as a Property, it is serialized as

{"Prop1":"foo","Prop2":"bar"}

，但是当它用作一字典键，它的方式，JSON.Net是能够正确地反序列化序列化

but when it is used as a Dictionary key, it is serialized in a way that JSON.Net is able to deserialize it properly.

当增加一个ToString（）方法来myvalue的，我能够创建一个文本表示（非JSON），允许用法词典关键，但不幸的是，我不能事后反序列化。即使添加JsonConverter为myvalue的没有帮助，因为它似乎是无法处理非JSON作为源格式（另外，当作为属性序列化，这是JSON，因此转换器将需要以某种方式处理这两种）。

When adding a ToString() method to MyValue, I am able to create a text representation (non-JSON) that allows the usage as Dictionary key but unfortunately, I am not able to deserialize it afterwards. Even adding a JsonConverter for MyValue did not help because it seems to be unable to handle non-JSON as source format (and additionally, when serialized as a property, it IS json, so the converter would need to handle both somehow).

推荐答案

你可以做的是序列化和反序列化你的字典在代理 KeyValuePair<字符串，字符串> 阵列，像这样：

What you could do is serialize and deserialize your dictionary in a proxy KeyValuePair<string, string> array, like so:

[DataContract]
public class MyContainer
{
    public MyContainer() {
        this.Dictionary = new Dictionary<MyValue, int>();
    }

    [DataMember]
    public MyValue MyValue { get; set; }

    [IgnoreDataMember]
    public Dictionary<MyValue, int> Dictionary { get; set; }

    [DataMember(Name="Dictionary")]
    private KeyValuePair<MyValue, int> [] SerializedDictionary
    {
        get
        {
            if (Dictionary == null)
                return null;
            return Dictionary.ToArray();
        }
        set
        {
            if (value == null)
            {
                Dictionary = null;
            }
            else
            {
                Dictionary = value.ToDictionary(pair => pair.Key, pair => pair.Value);
            }
        }
    }
}

（在这里，我使用了 DataContract 属性，但我可以很容易地使用了 [JsonIgnore] 和 [JsonProperty（说文解字））

(Here I'm using the DataContract attributes, but I could just as easily have used [JsonIgnore] and [JsonProperty("Dictionary")])

因此，为了测试这个（假设你已经正确地覆盖的GetHashCode（）和等于（）在 myvalue的，您需要为了使用它作为一个字典的键）做的，我做了以下内容：

So, to test this (and assuming that you have properly overridden GetHashCode() and Equals() on MyValue, which you need to do in order to use it as a dictionary key), I did the following:

public static class TestDictionaryJson
{
    public static void Test()
    {
        var dict = new Dictionary<MyValue, int>();
        dict[(new MyValue("A", "A"))] = 1;
        dict[(new MyValue("B", "B"))] = 2;

        var myContainer = new MyContainer() { MyValue = new MyValue("A Property", "At the top level"), Dictionary = dict };

        var json = JsonConvert.SerializeObject(myContainer, Formatting.Indented);

        Debug.WriteLine(json);

        try
        {
            var newContainer = JsonConvert.DeserializeObject<MyContainer>(json);
        }
        catch (Exception ex)
        {
            Debug.Assert(false, ex.ToString()); // No assert - no exception is thrown.
        }

        try
        {
            var dictjson = JsonConvert.SerializeObject(dict, Formatting.Indented);
            Debug.WriteLine(dictjson);
            var newDict = JsonConvert.DeserializeObject<Dictionary<MyValue, int>>(dictjson);
        }
        catch (Exception ex)
        {
            Debug.WriteLine("Caught expected exception deserializing dictionary directly: " + ex.ToString());
        }
    }
}

果然，没有异常反序列化的容器，但有已的直接反序列化的字典。而下面的JSON是为容器创建：

Sure enough, there was no exception deserializing the container, but there was deserializing the dictionary directly. And the following JSON was created for the container:

{
  "MyValue": {
    "Prop1": "A Property",
    "Prop2": "At the top level"
  },
  "Dictionary": [
    {
      "Key": {
        "Prop1": "A",
        "Prop2": "A"
      },
      "Value": 1
    },
    {
      "Key": {
        "Prop1": "B",
        "Prop2": "B"
      },
      "Value": 2
    }
  ]
}

这是你想要的吗？

更新

或者，如果你不喜欢的代理阵列，可以应用以下 JsonConverterAttribute 来的每词典属性来获得同样的结果：

Or, if you don't like the proxy arrays, you could apply the following JsonConverterAttribute to each and every Dictionary property to get the same result:

public class MyContainer
{
    public MyContainer()
    {
        this.Dictionary = new Dictionary<MyValue, int>();
    }

    public MyValue MyValue { get; set; }

    [JsonConverter(typeof(DictionaryToArrayConverter<MyValue, int>))]
    public Dictionary<MyValue, int> Dictionary { get; set; }
}

public class DictionaryToArrayConverter<TKey, TValue> : JsonConverter
{
    public override bool CanConvert(Type objectType)
    {
        return objectType == typeof(Dictionary<TKey, TValue>);
    }

    public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
    {
        KeyValuePair<TKey, TValue>[] pairs;

        JToken token = JToken.Load(reader);
        if (token.Type == JTokenType.Array)
        {
            pairs = token.ToObject<KeyValuePair<TKey, TValue>[]>(serializer);
        }
        else
        {
            JArray array = new JArray();
            array.Add(token);
            pairs = token.ToObject<KeyValuePair<TKey, TValue>[]>(serializer);
        }
        if (pairs == null)
            return null;
        return pairs.ToDictionary(pair => pair.Key, pair => pair.Value);
    }

    public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)
    {
        if (value == null)
            return;
        var pairs = ((IDictionary<TKey, TValue>)value).ToArray();
        serializer.Serialize(writer, pairs);
    }
}

更新

作为替代方案，你可以封你的 myvalue的类，并附加一个适当的 TypeConverterAttribute 从与放大器转换;为字符串。 JSON.Net会选择这并使用它无论是字​​典的键和属性。该解决方案是，它是一个全球性的解决方案，使您无需使用代理服务器阵列或转换属性，每一个字典，简单但是，对于你的 myvalue的属性创建的JSON是不太你需要

As an alternative, you could seal your MyValue class and attach an appropriate TypeConverterAttribute for converting from & to a string. JSON.Net will pick this up and use it both for dictionary keys and properties. This solution is simpler in that it's a global solution so you don't need to use proxy arrays or converter properties for each and every dictionary, however the JSON created for your MyValue properties isn't quite what you require.

这样：

public class MyValueConverter : TypeConverter
{
    public override bool CanConvertFrom(ITypeDescriptorContext context,
       Type sourceType)
    {
        if (sourceType == typeof(string))
        {
            return true;
        }
        return base.CanConvertFrom(context, sourceType);
    }

    public override object ConvertFrom(ITypeDescriptorContext context,
       CultureInfo culture, object value)
    {
        if (value is string)
        {
            // Cannot do JsonConvert.DeserializeObject here because it will cause a stackoverflow exception.
            using (var reader = new JsonTextReader(new StringReader((string)value)))
            {
                JObject item = JObject.Load(reader);
                if (item == null)
                    return null;
                MyValue myValue = new MyValue();
                var prop1 = item["Prop1"];
                if (prop1 != null)
                    myValue.Prop1 = prop1.ToString();
                var prop2 = item["Prop2"];
                if (prop2 != null)
                    myValue.Prop2 = prop2.ToString();
                return myValue;
            }
        }
        return base.ConvertFrom(context, culture, value);
    }

    public override object ConvertTo(ITypeDescriptorContext context,
       CultureInfo culture, object value, Type destinationType)
    {
        if (destinationType == typeof(string))
        {
            MyValue myValue = (MyValue)value;

            // Cannot do JsonConvert.SerializeObject here because it will cause a stackoverflow exception.
            StringBuilder sb = new StringBuilder();
            using (StringWriter sw = new StringWriter(sb, CultureInfo.InvariantCulture))
            using (JsonTextWriter jsonWriter = new JsonTextWriter(sw))
            {
                jsonWriter.WriteStartObject();
                jsonWriter.WritePropertyName("Prop1");
                jsonWriter.WriteValue(myValue.Prop1);
                jsonWriter.WritePropertyName("Prop2");
                jsonWriter.WriteValue(myValue.Prop2);
                jsonWriter.WriteEndObject();

                return sw.ToString();
            }
        }
        return base.ConvertTo(context, culture, value, destinationType);
    }
}

[TypeConverter(typeof(MyValueConverter))]
public class MyValue
{
    public MyValue()
    {
    }

    public MyValue(string prop1, string prop2)
    {
        this.Prop1 = prop1;
        this.Prop2 = prop2;
    }

    public String Prop1 { get; set; }
    public String Prop2 { get; set; }

    public override bool Equals(object obj)
    {
        if (ReferenceEquals(this, obj))
            return true;
        else if (ReferenceEquals(obj, null))
            return false;
        if (GetType() != obj.GetType())
            return false;
        var other = (MyValue)obj;
        return Prop1 == other.Prop1 && Prop2 == other.Prop2;
    }

    public override int GetHashCode()
    {
        unchecked
        {
            uint code = 0;
            if (Prop1 != null)
                code ^= (uint)Prop1.GetHashCode();
            code = (code << 16) | (code >> 16);
            if (Prop2 != null)
                code ^= (uint)Prop2.GetHashCode();
            return (int)code;
        }
    }

    public override string ToString()
    {
        return TypeDescriptor.GetConverter(GetType()).ConvertToString(this);
    }

    public static bool operator ==(MyValue first, MyValue second)
    {
        if (ReferenceEquals(first, null))
            return ReferenceEquals(second, null);
        return first.Equals(second);
    }

    public static bool operator !=(MyValue first, MyValue second)
    {
        return !(first == second);
    }
}

属性，并使用这个类字典，现在可以不用连载使用任何代理阵列。例如，序列化和反序列化以下内容：

Properties and dictionaries using this class can now be serialized without the use of any proxy arrays. For instance, serializing and deserializing the following:

public class MyContainer
{
    public MyContainer()
    {
        this.Dictionary = new Dictionary<MyValue, int>();
    }

    public MyValue MyValue { get; set; }

    public Dictionary<MyValue, int> Dictionary { get; set; }
}

提供了以下JSON时，序列化：

Gives the following JSON when serialized:

{
  "MyValue": "{\"Prop1\":\"A Property\",\"Prop2\":\"At the top level\"}",
  "Dictionary": {
    "{\"Prop1\":\"A\",\"Prop2\":\"A\"}": 1,
    "{\"Prop1\":\"B\",\"Prop2\":\"B\"}": 2
  }
}

（引号是逃跑，因为它们嵌入在JSON，而不是JSON的一部分）

(the quotes are escaped since they are embedded in the JSON, not part of the JSON.)

晚更新 - 创建一个通用的的TypeConverter 的字典键

Late Update - creating a generic TypeConverter for dictionary keys

这有可能创建一个通用的的TypeConverter ，对于任何工作一般指定类型通过使用合适的合同解析器：

It's possible to create a generic TypeConverter that works for any generically specified type by using an appropriate contract resolver:

public class NoTypeConverterContractResolver : DefaultContractResolver
{
    readonly Type type;

    public NoTypeConverterContractResolver(Type type)
        : base()
    {
        if (type == null)
            throw new ArgumentNullException();
        if (type == typeof(string) || type.IsPrimitive)
            throw new ArgumentException("type == typeof(string) || type.IsPrimitive");
        this.type = type;
    }

    protected override JsonContract CreateContract(Type objectType)
    {
        if (type.IsAssignableFrom(objectType))
        {
            // Replaces JsonStringContract for the specified type.
            var contract = this.CreateObjectContract(objectType);
            return contract;
        }
        return base.CreateContract(objectType);
    }
}

public class GenericJsonTypeConverter<T> : TypeConverter
{
    // As of 7.0.1, Json.NET suggests using a static instance for "stateless" contract resolvers, for performance reasons.
    // http://www.newtonsoft.com/json/help/html/ContractResolver.htm
    // http://www.newtonsoft.com/json/help/html/M_Newtonsoft_Json_Serialization_DefaultContractResolver__ctor_1.htm
    // "Use the parameterless constructor and cache instances of the contract resolver within your application for optimal performance."
    static NoTypeConverterContractResolver contractResolver;

    static NoTypeConverterContractResolver ContractResolver
    {
        get
        {
            if (contractResolver == null)
                Interlocked.CompareExchange(ref contractResolver, new NoTypeConverterContractResolver(typeof(T)), null);
            return contractResolver;
        }
    }

    public override bool CanConvertFrom(ITypeDescriptorContext context,
       Type sourceType)
    {
        if (sourceType == typeof(string))
        {
            return true;
        }
        return base.CanConvertFrom(context, sourceType);
    }

    public override object ConvertFrom(ITypeDescriptorContext context,
       CultureInfo culture, object value)
    {
        if (value is string)
        {
            using (var reader = new JsonTextReader(new StringReader((string)value)))
            {
                var obj = JsonSerializer.Create(new JsonSerializerSettings { ContractResolver = ContractResolver }).Deserialize<T>(reader);
                return obj;
            }
        }
        return base.ConvertFrom(context, culture, value);
    }

    public override object ConvertTo(ITypeDescriptorContext context, CultureInfo culture, object value, Type destinationType)
    {
        if (destinationType == typeof(string))
        {
            StringBuilder sb = new StringBuilder();
            using (StringWriter sw = new StringWriter(sb, CultureInfo.InvariantCulture))
            using (JsonTextWriter jsonWriter = new JsonTextWriter(sw))
            {
                JsonSerializer.Create(new JsonSerializerSettings { ContractResolver = ContractResolver }).Serialize(jsonWriter, value);
            }
            return sb.ToString();
        }
        return base.ConvertTo(context, culture, value, destinationType);
    }
}

然后如下应用到你的类：

Then apply it to your class as follows:

[TypeConverter(typeof(GenericJsonTypeConverter<MyValue>))]
public class MyValue
{

}

这篇关于在字典与JSON.Net复杂类型的具体使用序列化的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！