Workaround for providing support for System.Exception with System.Text.Json

[snjosephms]

We are migrating our code base from Newtonsoft to System.Text.Json. While testing this migration effort, we have encountered errors while working with System.Exception objects.

SerializedData Text: We see the following data in the serialized data created using System.Text.Json

{
"Status": 0,
"Exception": {
"Message": "TestExceptionMessag",
"Data": {},
"HResult": -2146233088
},
"SourceService": 1,
"RequestId": "97f534a6-cfad-4d5f-934a-7298d27288a4",
"Type": "ProvisionOC_Response",
"RetryCount": 0,
"IsRetryable": false,
"ResubmitRetryCount": 0
}

Issue:
The de-serialized data does not contain the Message text correctly. Message from deserialized object is "Exception of type 'System.Exception' was thrown."

Can you please share a workaround for providing support for System.Exception type with System.Text.Json?

[ghost]

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Issue Details

---

We are migrating our code base from Newtonsoft to System.Text.Json. While testing this migration effort, we have encountered errors while working with System.Exception objects.

SerializedData Text: We see the following data in the serialized data created using System.Text.Json

{
"Status": 0,
"Exception": {
"Message": "TestExceptionMessag",
"Data": {},
"HResult": -2146233088
},
"SourceService": 1,
"RequestId": "97f534a6-cfad-4d5f-934a-7298d27288a4",
"Type": "ProvisionOC_Response",
"RetryCount": 0,
"IsRetryable": false,
"ResubmitRetryCount": 0
}

Issue:
The de-serialized data does not contain the Message text correctly. Message from deserialized object is "Exception of type 'System.Exception' was thrown."

Can you please share a workaround for providing support for System.Exception type with System.Text.Json?

Author:	snjosephms
Assignees:	-
Labels:	area-System.Text.Json
Milestone:	-

[krwq]

You will need to write JsonConverter and factory for exceptions because Message doesn't have a setter (unless you're fine with setting that by reflection then you can also workaround it with contract model and providing Set for Message property). If exception is your own implementation then you can use JsonConstructor attribute and put it on the constructor which takes message

[snjosephms]

Exception is not our own implementation. We are using the System.Exception class

[eiriktsarpalis]

@snjosephms could you share the expected serialization format?

[eiriktsarpalis]

I understand that System.Text.Json does not roundtrip Exception.Message but Json.NET does. What I would need to know however is the JSON being produced by Json.NET currently.

[snjosephms]

Ok, I get your question now. I'll revert on this.

[snjosephms]

Json produced by Newtonsoft: "{"Status":"NotStarted","Exception":{"ClassName":"System.Exception","Message":"TestExceptionMessage","Data":{"$type":"System.Collections.ListDictionaryInternal, mscorlib"},"InnerException":null,"HelpURL":null,"StackTraceString":null,"RemoteStackTraceString":null,"RemoteStackIndex":0,"ExceptionMethod":null,"HResult":-2146233088,"Source":null,"WatsonBuckets":null},"SourceService":"ChannelConnector","RequestId":"a4f8402f-d0b6-4f64-8d59-1f11e949ba5b","Type":"PROVISIONOC_RESPONSE","Version":null,"RetryCount":0,"IsRetryable":false,"ResubmitRetryCount":0,"OrgInfo":null}"
Json produced by STJ: "{"Status":0,"Exception":{"Message":"TestExceptionMessage","Data":{},"HResult":-2146233088},"SourceService":1,"RequestId":"a4f8402f-d0b6-4f64-8d59-1f11e949ba5b","Type":"ProvisionOC_Response","RetryCount":0,"IsRetryable":false,"ResubmitRetryCount":0}"

[snjosephms]

@eiriktsarpalis just wanted to follow up on this thread.

[eiriktsarpalis]

I see, so you're relying on your Exceptions' ISerializable output. STJ does not support ISerializable since it is associated with security flaws and is subject to deprecation in future release in .NET. That being said, it might be possible to write a custom converter for exceptions as follows:

public class ExceptionConverter : JsonConverter<Exception>
{
    public override bool CanConvert(Type type) => typeof(Exception).IsAssignableFrom(type);
    public override Exception Read(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
    {
        // Create a SerializationInfo object
        var info = new SerializationInfo(typeToConvert, new FormatterConverter());

        // Populate it with JSON properties
        while (reader.Read() && reader.TokenType != JsonTokenType.EndObject)
        {
            string propertyName = reader.GetString()!;
            reader.Read();
            object? value = JsonSerializer.Deserialize(ref reader, typeof(object), options);
            info.AddValue(propertyName, value);
        }

        // Use it to construct your object
        return (Exception)Activator.CreateInstance(typeToConvert, info, new StreamingContext())!;
    }

    public override void Write(Utf8JsonWriter writer, Exception value, JsonSerializerOptions options)
    {
        // Create a SerializationInfo object
        var info = new SerializationInfo(value.GetType(), new FormatterConverter());

        // Populate it with your object's fields
        value.GetObjectData(info, new StreamingContext());

        // Write it as JSON properties
        writer.WriteStartObject();

        // Write SerializationEntries as JSON properties
        foreach (SerializationEntry entry in info)
        {
            writer.WritePropertyName(entry.Name);
            JsonSerializer.Serialize(writer, entry.Value, options);
        }

        writer.WriteEndObject();
    }
}