public static void WriteJson(this IJsonSerializable obj, JsonTextWriter writer)
{
writer.WriteStartObject();
var polymorph = obj as IPolymorphable;
if (polymorph != null)
{
writer.WritePropertyName("classId");
writer.WriteValue(polymorph.GetClassId());
// var f = writer.Formatting;
// writer.Formatting = Formatting.None;
// writer.WritePropertyName("className");
// writer.WriteValue(obj.GetType().Name);
// writer.Formatting = f;
}
obj.WriteJsonFields(writer);
writer.WriteEndObject();
}