Can I control what subtype to use when deserializing a JSON string?

Question

I'm working with Facebook API and it's search method returns a JSON response like this:

{
   "data": [
      {
         "id": "1",
         "message": "Heck of a babysitter...",
         "name": "Baby eating a watermelon",
         "type": "video"
      },
      {
         "id": "2",
         "message": "Great Produce Deals",
         "type": "status"
      }
   ]
}

I have a class structure similar to this:

[DataContract]
public class Item
{
    [DataMember(Name = "id")]
    public string Id { get; set; }
}

[DataContract]
public class Status : Item
{
    [DataMember(Name = "message")]
    public string Message { get; set; }
}

[DataContract]
public class Video : Item
{
    [DataMember(Name = "string")]
    public string Name { get; set; }

    [DataMember(Name = "message")]
    public string Message { get; set; }
}

[DataContract]
public class SearchResults
{
    [DataMember(Name = "data")]
    public List<Item> Results { get; set; }
}

How can I use correct subclass based on that type attribute?

Answer 1

If you use the

System.Web.Script.Serialization.JavaScriptSerializer

you can use the overload in the constructor to add your own class resolver:

JavaScriptSerializer myserializer = new JavaScriptSerializer(new FacebookResolver());

An example how to implement this can be found here on SO: http://stackoverflow.com/questions/1027107/javascriptserializer-with-custom-type

But you should replace the

"type": "video"

part to

"__type": "video"

since this is the convention for the class.

Here is an example:

public class FacebookResolver : SimpleTypeResolver
{
    public FacebookResolver() { }
    public override Type ResolveType(string id)
    {
        if(id == "video") return typeof(Video);
        else if (id == "status") return typeof(Status)
        else return base.ResolveType(id);
    }
}