How to serialize/deserialize a custom collection with additional properties using Json.Net

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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}]

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);
    }
}

Then use it as follows:

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

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

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