Deserialize Json string with nested class of variable type [duplicate]

Question

maybe a similar question has already been answered somewhere else. But I've spent a lot of time to look for it and to try getting a solution. So I hope someone can help.

I have a class

public class SampleClass
{
   public int Id {get;set;}
   public string TypeName {get;set;}
   public BaseClass Data {get;set;}
}

Then I have several "data" classes derived from BaseClass, for example:

public class DataClass: BaseClass
{
    public string Name {get;set;}
    public string Address {get;set;}
}

Serialization works fine.

var sample = new SampleClass();
sample.Id = 1;
sample.TypeName = "DataClass";

var data = new DataClass();
data.Name = "Test";
data.Address = "Address";

sample.Data = data;

var jsonString = JsonConvert.SerializeObject(sample);

Result: {"Id":1,"TypeName":"DataClass","Data":{"Name":"Test","Address":"Address"}}

But the way back brings an empty "Data" property:

var backToObject = JsonConvert.DeserializeObject<SampleClass>(jsonString);

Is there a way to tell the Json converter that it should deserialize "Data" into the type given in "TypeName"?

Try to use type name handling newtonsoft.com/json/help/html/SerializeTypeNameHandling.htm — Paolo Iommarini
– Paolo Iommarini, Commented Aug 17, 2022 at 21:25
This post looks like it will assist you stackoverflow.com/questions/6904825/… — pelican_incident
– pelican_incident, Commented Aug 17, 2022 at 21:30
Is there a way to tell the Json converter that it should deserialize "Data" into the type given in "TypeName"? You can create a custom JsonConverter to deserialize your class hierarchy. Please see Deserializing polymorphic json classes without type information using json.net, Json.Net Serialization of Type with Polymorphic Child Object or How to implement custom JsonConverter in JSON.NET to deserialize a List of base class objects? for details. — dbc
– dbc, Commented Aug 17, 2022 at 22:20
That being said, it's better to put the TypeName property inside BaseClass rather than SampleClass so BaseClass is self-contained and can be reused elsewhere. — dbc
– dbc, Commented Aug 17, 2022 at 22:23

wwd · Accepted Answer · 2022-08-17 22:02:12Z

1

var data = new DataClass
{
    Name = "Test",
    Address = "Address"
};

var sample = new SampleClass
{
    Id = 1,
    TypeName = "DataClass"
};

sample.Data = data;

var jsonString = JsonConvert.SerializeObject(sample, new JsonSerializerSettings
{
    TypeNameHandling = TypeNameHandling.All
});

var backToObject = JsonConvert.DeserializeObject<SampleClass>(jsonString, new JsonSerializerSettings
{
    TypeNameHandling = TypeNameHandling.Auto
});

The deserialization result looks like:

[17:59:50 INF] {"Id": 1, "TypeName": "DataClass", "Data": {"Name": "Test", "Address": "Address", "$type": "DataClass"}, "$type": "SampleClass"}

answered Aug 17, 2022 at 22:02

wwd

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1 Comment

Belenos Over a year ago

That's quite a good approach. But in my case it doesn't work. The used type for the nested class comes from a separate assembly. So I need to "inject" the type into the (de)serializer. Is there a way to do this?

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