如何使用 Json.Net 序列化/反序列化具有附加属性的自定义集合 [英] How to serialize/deserialize a custom collection with additional properties using Json.Net

问题描述

我有一个自定义集合(实现 IList)，它有一些自定义属性，如下所示:

I have a custom collection (implements IList) which has some custom properties as shown below:

class FooCollection : IList<Foo> {

    private List<Foo> _foos = new List<Foo>();
    public string Bar { get; set; }        

    //Implement IList, ICollection and IEnumerable members...

}

当我序列化时，我使用以下代码:

When I serialize, I use the following code:

JsonSerializerSettings jss = new JsonSerializerSettings() {
    TypeNameHandling = TypeNameHandling.Auto
};
string serializedCollection = JsonConvert.SerializeObject( value , jss );

它正确序列化和反序列化所有集合项；但是，不考虑 FooCollection 类中的任何额外属性.

It serializes and deserializes all the collection items properly; however, any extra properties in the FooCollection class are not taken into account.

无论如何要将它们包含在序列化中?

Is there anyway to include them in the serialization?

推荐答案

问题如下:当一个对象实现了 IEnumerable 时，JSON.net 将其标识为一个值数组并序列化如下数组 Json 语法(不包括属性)，例如:

The problem is the following: when an object implements IEnumerable, JSON.net identifies it as an array of values and serializes it following the array Json syntax (that does not include properties), e.g. :

 [ {"FooProperty" : 123}, {"FooProperty" : 456}, {"FooProperty" : 789}]

如果你想序列化它保留属性，你需要通过定义一个自定义的JsonConverter来手动处理那个对象的序列化:

If you want to serialize it keeping the properties, you need to handle the serialization of that object by hand by defining a custom JsonConverter :

// intermediate class that can be serialized by JSON.net
// and contains the same data as FooCollection
class FooCollectionSurrogate
{
    // the collection of foo elements
    public List<Foo> Collection { get; set; }
    // the properties of FooCollection to serialize
    public string Bar { get; set; }
}

public class FooCollectionConverter : JsonConverter
{
    public override bool CanConvert(Type objectType)
    {
        return objectType == typeof(FooCollection);
    }

    public override object ReadJson(
        JsonReader reader, Type objectType, 
        object existingValue, JsonSerializer serializer)
    {
        // N.B. null handling is missing
        var surrogate = serializer.Deserialize<FooCollectionSurrogate>(reader);
        var fooElements = surrogate.Collection;
        var fooColl = new FooCollection { Bar = surrogate.Bar };
        foreach (var el in fooElements)
            fooColl.Add(el);
        return fooColl;
    }

    public override void WriteJson(JsonWriter writer, object value, 
                                   JsonSerializer serializer)
    {
        // N.B. null handling is missing
        var fooColl = (FooCollection)value;
        // create the surrogate and serialize it instead 
        // of the collection itself
        var surrogate = new FooCollectionSurrogate() 
        { 
            Collection = fooColl.ToList(), 
            Bar = fooColl.Bar 
        };
        serializer.Serialize(writer, surrogate);
    }
}

然后使用如下:

var ss = JsonConvert.SerializeObject(collection, new FooCollectionConverter());

var obj = JsonConvert.DeserializeObject<FooCollection>(ss, new FooCollectionConverter());

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