Serialize custom exception to JSON with web api

Question

I need to show custom property added to custom exception ModelException at the output json of my WebApi. So I created custom exception class as follows

 [Serializable]
public class ModelException : System.Exception
{
    private int exceptionCode;
    public int ExceptionCode
    {
        get
        {
            return exceptionCode;
        }
        set
        {
            exceptionCode = value;
        }
    }

    public ModelException() : base() { }

    public ModelException(string message) : base(message) { }

    public ModelException(string format, params object[] args) : base(string.Format(format, args)) { }

    public ModelException(string message, System.Exception innerException) : base(message, innerException) { }

    public ModelException(string format, System.Exception innerException, params object[] args) : base(string.Format(format, args), innerException) { }


    protected ModelException(SerializationInfo info, StreamingContext context)
        : base(info, context)
    {
        if (info != null)
        {
            int result = 0;
            int.TryParse(info.GetString("ExceptionCode"), out result);
            this.exceptionCode = result;
        }
    }

    [SecurityPermissionAttribute(SecurityAction.Demand, SerializationFormatter = true)]
    public override void GetObjectData(SerializationInfo info, StreamingContext context)
    {
        if (info != null)
        {
            info.AddValue("ExceptionCode", this.exceptionCode);
        }

        base.GetObjectData(info, context);
    }

    public ModelException(string message, int exceptionCode)
        : base(message)
    {
        this.exceptionCode = exceptionCode;
    }
}

then add the following configration to my WebApiConfig

config.Formatters.JsonFormatter.SerializerSettings.Formatting = Formatting.Indented;
config.Formatters.JsonFormatter.SerializerSettings.ContractResolver = new DefaultContractResolver()
        {
            IgnoreSerializableInterface = true
        };

the issue here is the new overidden constructor with SerializationInfo parameter is not fired and the newly custom property is not appear in the returned Json from WebApi

One of the mechanism that I use to achieve the same is using the Web API Error filters, which can intercept the call on exception and can be used to modify the Context.Response, with necessary exception information, check: asp.net/web-api/overview/error-handling/exception-handling — Mrinal Kamboj
– Mrinal Kamboj, Commented Jul 5, 2016 at 11:11
Don't you need to set IgnoreSerializableInterface = false instead? — dbc
– dbc, Commented Jul 5, 2016 at 11:15
@dbc yes i tried setting IgnoreSerializableInterface = false but nothing worked the custom property doesnt apear — Mohamed Salah
– Mohamed Salah, Commented Jul 5, 2016 at 12:34
@MrinalKamboj I tried adding custom filter to intercept the call on exception but with no luck to show the custom property in the final json — Mohamed Salah
– Mohamed Salah, Commented Jul 7, 2016 at 22:46

Mohamed Salah · Accepted Answer · 2016-07-09 10:46:47Z

Thanks to @MrinalKamboj

In order to change the output Json of Web API in the case of Exception. I did the following changes to solve this

Implement my Custom Exception (ModelException) as in my Question

as per @MrinalKamboj comment i created the following

public class NotImplExceptionFilterAttribute : ExceptionFilterAttribute 
{
    public override void OnException(HttpActionExecutedContext context)
    {
         if (context.Exception is ModelException)
         {
            ModelException exception = (ModelException)context.Exception;
            HttpError error = new HttpError();
            error.Add("Message", "An error has occurred.");
            error.Add("ExceptionMessage", exception.Message);
            error.Add("ExceptionCode", exception.ExceptionCode);
            error.Add("ExceptionType", exception.Source);
            error.Add("StackTrace", exception.StackTrace);

            context.Response = context.Request.CreateErrorResponse(HttpStatusCode.InternalServerError, error);
         }
    }
}

register the attribute to Web API as follows

config.Filters.Add(new NotImplExceptionFilterAttribute());

The explanation of the issue

I want to change the output json resulted from Web API this will not be applicable by just implementing ISerializable we need to intercept the exception and change the output response of the json using HTTPErorr

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Serialize custom exception to JSON with web api

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