如何将 JSON object 反序列化为使用派生类的 C# ZA2F2ED4F8EBC2CBB4C21A29DC40AB6？

Question

I have the following classes which I am serialising and deserialising to and from JSON using Json.NET :

public class Message
{
  public Guid MessageId { get; set; }
  public List<Task> Tasks { get; set; }
}

public class Task
{
  public int TaskId { get; set; }
}

public SomeTask : Task
{
  public string SomeTaskThing { get; set; }
  public List<string> Operations { get; set; }
}

public OtherTask : Task
{
  public int OtherTaskThing { get; set; }
  public List<int> MoreOtherTaskThings { get; set; }
}

A Message basically consists of a list of SomeTask and OtherTask Task s which I pass across the wire to a message processor that also knows about these classes.

When I serialise a Message I do the following:

string json = JsonConvert.SerializeObject(
        message, 
        Formatting.Indented, 
        new JsonSerializerSettings
          {
            TypeNameHandling = TypeNameHandling.Objects
          });

My derived classes are serialised as I would expect along with $type names embedded in the JSON.

However when I deserialise the JSON string back to a Message object the deserialiser doesn't rehydrate my derived class objects. I just get a list of the base class Task .

I thought $type added to the JSON string by using TypeNameHandling = TypeNameHandling.Objects might have provided a hint to the deserialiser about which classes to instantiate, but I was wrong.

What do I need to do to deserialise objects who's base class is Task and rehydrate the derived classes into the List<Task> ?

I'm limited to .NET Framework 3.5 for this project.

Answer 1

Make sure you are using the same JsonSerializerSettings to deserialize as well. It doesn't have to be the same instance but it must have TypeNameHandling = TypeNameHandling.Objects set in order to work on deserialization.