Json.NET simple interface serialization

Question

I'm trying to serialize the IAnimal instance object to json using Json.NET. Class structure:

public class Dog : IAnimal {
    public int Width { get; set; }
    public double Bark { get; set; }
}

public class Cat : IAnimal {
    public int Width { get; set; }
    public double Meow { get; set; }
}

public interface IAnimal {
    int Width { get; set; }
}

public class AnimalContainer {
    public IAnimal Animal { get; set; }
}

Tried this way (please notice I use 'TypeNameHandling.Auto' as I found in other threads):

public void IAnimal_ShouldBeJsonSerializable() {
        var animal = new AnimalContainer {Animal = new Dog {Bark = 5, Width = 2}};
        var json = JsonConvert.SerializeObject(animal,
            new JsonSerializerSettings{TypeNameHandling = TypeNameHandling.Auto});
        var deserializedAnimal = JsonConvert.DeserializeObject<AnimalContainer>(json);
    }

but is throwing me exception that "Could not create an instance of type IAnimal, Type is an interface or abstract class and cannot be instantiated". But the json contains the concrete type information!

How can I make it work?

stackoverflow.com/questions/24644464/…

Adam Rackis
– Adam Rackis

2014-10-27 23:16:38 +00:00
Commented Oct 27, 2014 at 23:16 — Adam Rackis
– Adam Rackis, Commented Oct 27, 2014 at 23:16
Your Animals have Width???

Shiva
– Shiva

2014-10-27 23:27:48 +00:00
Commented Oct 27, 2014 at 23:27 — Shiva
– Shiva, Commented Oct 27, 2014 at 23:27

Brian Rogers · Accepted Answer · 2014-10-27 23:25:20Z

2

It does not look like you are passing the serializer settings to your DeserializeObject call. You need to include the TypeNameHandling both on Serialize and Deserialize.

var animal = new AnimalContainer { Animal = new Dog { Bark = 5, Width = 2 } };
var settings = new JsonSerializerSettings { TypeNameHandling = TypeNameHandling.Auto };
var json = JsonConvert.SerializeObject(animal, settings);
var deserializedAnimal = JsonConvert.DeserializeObject<AnimalContainer>(json, settings);
Console.WriteLine(deserializedAnimal.Animal.GetType().Name);

edited Oct 27, 2014 at 23:25

answered Oct 27, 2014 at 23:17

Brian Rogers

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2 Comments

mbudnik Over a year ago

Hey, thanks for fast response. It works when animal is an interface. What about an abstract class? Getting the same exception again.

Brian Rogers Over a year ago

Should still work; I just tried it by creating an abstract BaseAnimal class and making both Dog and Cat inherit from it. (I moved the Width property to the base.) Then I changed the Animal property in the AnimalContainer to be a `BaseAnimal'. I ran the above serialize/deserialize code, and it worked fine.

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