c# - Deserialize json with known and unknown fields

Question

Given following json result: The default json result has a known set of fields:

{
    "id": "7908",
    "name": "product name"
}

But can be extended with additional fields (in this example _unknown_field_name_1 and _unknown_field_name_2) of which the names are not known when requesting the result.

{
    "id": "7908",
    "name": "product name",
    "_unknown_field_name_1": "some value",
    "_unknown_field_name_2": "some value"
}

I would like the json result to be serialized and deserialized to and from a class with properties for the known fields and map the unknown fields (for which there are no properties) to a property (or multiple properties) like a dictionary so they can be accessed and modified.

public class Product
{
    public string id { get; set; }
    public string name { get; set; }
    public Dictionary<string, string> fields { get; set; }
}

I think I need a way to plug into a json serializer and do the mapping for the missing members myself (both for serialize and deserialize). I have been looking at various possibilities:

• json.net and custom contract resolvers (can't figure out how to do it)
• datacontract serializer (can only override onserialized, onserializing)
• serialize to dynamic and do custom mapping (this might work, but seems a lot of work)
• let product inheriting from DynamicObject (serializers work with reflection and do not invoke the trygetmember and trysetmember methods)

I'm using restsharp, but any serializer can be plugged in.

Oh, and I cannot change the json result, and this or this didn't help me either.

Update: This looks more like it: http://geekswithblogs.net/DavidHoerster/archive/2011/07/26/json.net-custom-convertersndasha-quick-tour.aspx

Answer 1

An even easier option to tackling this problem would be to use the JsonExtensionDataAttribute from JSON .NET

public class MyClass
{
   // known field
   public decimal TaxRate { get; set; }

   // extra fields
   [JsonExtensionData]
   private IDictionary<string, JToken> _extraStuff;
}

There's a sample of this on the project blog here

UPDATE Please note this requires JSON .NET v5 release 5 and above