JSON.NET is ignoring properties in types derived from System.Exception. Why?

Question

I want to JSON serialize a custom exception object which inherits System.Exception. JsonConvert.SerializeObject seems to ignore properties from the derived type. The problem can be illustrated very simply:

class MyException : Exception {
    public string MyProperty { get; set; }
}

class Program {
    static void Main(string[] args) {
        Console.WriteLine(JsonConvert.SerializeObject(new MyException {MyProperty = "foobar"}, Formatting.Indented));
        //MyProperty is absent from the output. Why?
        Console.ReadLine();
    }
}

I've tried adding the DataContract and DataMember attributes in the correct places. They don't help. How do I get this to work?

I found the same solution as Thomas. Extending the ISerializable implementation is better than ignoring it. Consider, ISerializable was implemented by the creator of the base class for a reason. Ignoring it bypasses all of their work. When I used IgnoreSerializableInterface with my exception, the ClassName property was not included. As a result, I was unable to de-serialize it later. Extending GetObjectData and the constructor works perfectly. (I would have left this as a comment, but I have no reputation yet.) — Jack Whipnert
– Jack Whipnert, Commented Feb 8, 2017 at 15:58

Mike Zboray · Accepted Answer · 2014-11-29 00:04:42Z

19

Because Exception implements ISerializable, Json.Net uses that to serialize the object by default. You can tell it to ignore ISerializable like so:

var settings = new JsonSerializerSettings() {
    Formatting = Formatting.Indented,
    ContractResolver = new DefaultContractResolver() { 
        IgnoreSerializableInterface = true 
    } 
};
Console.WriteLine(JsonConvert.SerializeObject(new MyException {MyProperty = "foobar"}, settings));

answered Nov 29, 2014 at 0:04

Mike Zboray

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3 Comments

Maxime Rossini Over a year ago

This will cause errors because exceptions have self-referencing members. You have to specify ReferenceLoopHandling = ReferenceLoopHandling.Ignore in the JsonSerializerSettings in addition to your code. Anyway I think serializing an exception this way is a really bad idea as the TargetSite property can generate a REALLY heavy string (like several MBytes).

Ivan Kochurkin Over a year ago

@MaximeRossini, you are right. But it's possible to use DynamicContractResolver for ignoring TargetSite property.

pushkin Over a year ago

@MaximeRossini FYI, TargetSite is no longer included when serializing as per this PR

Allon Guralnek · Accepted Answer · 2015-09-03 10:10:19Z

8

You could also add and retrieve a specific object into the System.Runtime.Serialization.SerializationInfo store by overriding the GetObjectData method and the ctor(SerializationInfo, StreamingContext):

public class MyCustomException : Exception
{
    public string MyCustomData { get; set; }

    protected MyCustomException (SerializationInfo info, StreamingContext context) : base(info, context)
    {
        MyCustomData = info.GetString("MyCustomData");
    }

    public override void GetObjectData(SerializationInfo info, StreamingContext context)
    {
        base.GetObjectData(info, context);
        info.AddValue("MyCustomData", MyCustomData);
    }
}

This way the MyCustomObject property will get included in serialization and deserialization.

edited Sep 3, 2015 at 10:10

Allon Guralnek

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answered Jun 13, 2015 at 14:28

Thomas C. G. de Vilhena

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1 Comment

dasch88 Over a year ago

In addition to this, I needed to add the [Serializable] attribute to the derived exception class for it to work

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