The solution to this problem is to configure the deserializer to use the type information in the json. It is not used by default.
Serialization is done this way:
Newtonsoft.Json.JsonSerializer serializer = new Newtonsoft.Json.JsonSerializer();
serializer.Converters.Add(new Newtonsoft.Json.Converters.JavaScriptDateTimeConverter());
serializer.NullValueHandling = Newtonsoft.Json.NullValueHandling.Ignore;
serializer.TypeNameHandling = Newtonsoft.Json.TypeNameHandling.Auto;
serializer.Formatting = Newtonsoft.Json.Formatting.Indented;
using (StreamWriter sw = new StreamWriter(fileName))
using (Newtonsoft.Json.JsonWriter writer = new Newtonsoft.Json.JsonTextWriter(sw))
{
serializer.Serialize(writer, obj, typeof(MyDocumentType));
}
At deserialization, the settings for TypeNameHandling must be set:
MyDocumentType obj = Newtonsoft.Json.JsonConvert.DeserializeObject<MyDocumentType>(File.ReadAllText(fileName), new Newtonsoft.Json.JsonSerializerSettings
{
TypeNameHandling = Newtonsoft.Json.TypeNameHandling.Auto,
NullValueHandling = Newtonsoft.Json.NullValueHandling.Ignore,
});