Serializing properties of derived type from base type collection with NewtonSoft Json.NET

4
votes

Update: solved! It seems like Json.NET does include derived type properties by default, but they were not included because of an error in my code where the derived type was overwritten by a base type.

I am currently working on a project for school, and I stumbled upon a problem.

I need to serialize an object to Json, which I do using Newtonsoft Json.NET. The object I am trying to serialize has a List of objects of a certain base class, but the objects in that List are of derived types with their own unique properties.

Currently, only the properties of the base class are included in the resulting Json. If it's possible, I'd like the Json converter to detect of which derived class the objects in the collection are, and to serialize their unique properties.

Below some code as an example of what I'm doing.

Classes I use:

public class WrappingClass
{
    public string Name { get; set; }
    public List<BaseClass> MyCollection { get; set; }
}

public class BaseClass
{
    public string MyProperty { get; set; }
}

public class DerivedClassA : BaseClass
{
    public string AnotherPropertyA { get; set; }
}

public class DerivedClassB : BaseClass
{
    public string AnotherPropertyB { get; set; }
}

Serializing some dummy objects:

WrappingClass wrapperObject = new WrappingClass
{
    Name = "Test name",
    MyCollection = new List<BaseClass>();
};

DerivedClassA derivedObjectA = new DerivedClassA
{
    MyProperty = "Test my MyProperty A"
    AnotherPropertyA = "Test AnotherPropertyA"
};

DerivedClassB derivedObjectB = new DerivedClassB
{
    MyProperty = "Test my MyProperty B"
    AnotherPropertyB = "Test AnotherPropertyB"
};

wrapperObject.MyCollection.Add(derivedObjectA);
wrapperObject.MyCollection.Add(derivedObjectB);

var myJson = JsonConvert.SerializeObject(wrapperObject);

The Json that would currently be generated:

{"Name":"Test name","MyCollection":[{"MyProperty":"Test my MyProperty A"}{"MyProperty":"Test my MyProperty B"}]}

The Json I want:

{"Name":"Test name","MyCollection":[{"MyProperty":"Test my MyProperty A","AnotherPropertyA":"Test AnotherPropertyA"},{"MyProperty":"Test my MyProperty B","AnotherPropertyB":"Test AnotherPropertyB"}]}

Any ideas? Thank you!

2
c#jsoninheritanceserializationjson.net
I think something is missing in your example code that is causing this behavior. Running your example code gives the following json: { "Name": "Test name", "MyCollection": [ { "AnotherPropertyA": "Test AnotherPropertyA", "MyProperty": "Test my MyProperty A" }, { "AnotherPropertyB": "Test AnotherPropertyB", "MyProperty": "Test my MyProperty B" } ] } – redrobot
I think the answer to this is going to be fairly involved and require you to cast the objects to their deriving type before deserializing them. I'm reading the docs, and if I can't find some easy option I might write custom serializer that does the type of thing I'm referring to above. – evanmcdonnal
Those probably aren't your actual classes. In your real code are there annotations on any properties/classes used here? I'm talking about things like [DataContract] [DataMember] [("jsonpropert....")] ect if so please include them. – evanmcdonnal

2 Answers

2
votes

The default behavior of json.NET is to include all properties on derived types. The only reason you would not be getting them is if you have defined a [DataContract] on the base type which you have not extended to your derived types or if you have something like optin serialization ect.

-1
votes

Decorate the properties with Ignore attribute if you dont want them serialized like 

public class DerivedClassA : BaseClass
{
    [JsonIgnore]
    public string AnotherPropertyA { get; set; }
}