Catch json.net serialization errors

Question

I'm working on a web api using dotnet core 2.2 and we want to catch serialization exception and return a 400 badRequest to distinguish from the validation errors 422UnprocessableEntity. We tried to create an exception handler

public void JsonSerializerExceptionHandler(object sender, Newtonsoft.Json.Serialization.ErrorEventArgs args)
    {
        args.ErrorContext.Handled = true;
        var errorContext = args.ErrorContext;
        if (errorContext == null)
        {
            return;
        }

        var error = errorContext.Error;
        throw new SerializationException(error.Message, error.InnerException);
    }

but when it throw it throw an other Exception of type InvalidOperationException with message

Current error context error is different to requested error.

We tried different approach but can't find a solution. Can someone help?

Im unsure why you are trying to achieve this. I would just wrap my serialization code in a try catch and if you are looking for serialization errors just add a specific catch block for that. You can go as far as writing a middleware that specifically catches these anywhere in the MVC layer. — cl0ud
– cl0ud, Commented Feb 7, 2019 at 8:03
We are trying to achieve this because it is a request from the client, Json.net does not throw exceptions by itself, if I remove the last line it doesn't throw at all. — Pierre Côté
– Pierre Côté, Commented Feb 7, 2019 at 12:50

Adrian Iftode · Accepted Answer · 2021-04-14 08:46:23Z

1

Maybe my solution will be useful for somebody. I need to catch JSON.NET serialization or deserialization exception and handle it in my .NET Core middleware.

Add rethrow json.net exception in JSON.NET SerializerSettings

services.AddControllers().AddNewtonsoftJson(options => {


    //your options here
 

    options.SerializerSettings.Error += (sender, args) => throw args.ErrorContext.Error;

});

Add catch on middleware handler and override JsonSerializationException:

if (exception is JsonSerializationException)
{
    var exceptionMessage = exception.InnerException != null ? 
       exception.InnerException.Message : exception.Message;

    exception = new BadRequestException(ApiErrorCode.InvalidResourceModel,
      exceptionMessage);
}

edited Apr 14, 2021 at 8:46

Adrian Iftode

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answered Jun 4, 2020 at 14:41

Andrey Ravkov

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1 Comment

Brian Over a year ago

I have occasionally hit issues where an action parameter was null. They are frustrating to debug, but so far have been very straight-forward. This one was very difficult, so I went in search of info on how to see deserialization error details. This post was VERY useful, thank you! Upvoted.

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Catch json.net serialization errors

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Add rethrow json.net exception in JSON.NET SerializerSettings

Add catch on middleware handler and override JsonSerializationException:

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Add rethrow json.net exception in JSON.NET SerializerSettings

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