CODEWITHSUNDEEP
c#json.netazureservicebus
Endovelicvs
Endovelicvs

Reputation: 119

How to handle null values using DeserializeObject method

I am using Newtonsoft.Json to deserialize an object. And I am getting the following Exception:

Newtonsoft.Json.JsonSerializationException
  HResult=0x80131500
  Message=Error converting value {null} to type 'System.DateTime'. Path 'StartDate', line 1, position 62.
  Source=Newtonsoft.Json
  
Inner Exception 1:
InvalidCastException: Null object cannot be converted to a value type.

The original json has null values:

{
  "StartDate": null,
  "EndDate": null
}

But I am supplying settings to JsonConvert.DeserializeObject to avoid the null values, as mentioned here and here:

var convertedMessage = JsonConvert.DeserializeObject<T>(
                Encoding.UTF8.GetString(message.Body),
                new JsonSerializerSettings { NullValueHandling = NullValueHandling.Ignore });

Any idea why it keeps throwing this exception?

The code is running fine if an actual date value is provided.

More background on the code, the message.Body is the body of a message received through a service bus (class Microsoft.Azure.ServiceBus.Message). And applying the GetString method to it returns the same string as in the message sent.

A runnable sample of the code:

using System;
using System.Text;
using Microsoft.Azure.ServiceBus;
using Newtonsoft.Json;


namespace ConsoleApp1
{
    public class Program
    {
        public static void Main(string[] args)
        {
            Console.WriteLine(DeserializeJsonMessage<SampleMessage>(
                new Message(Encoding.UTF8.GetBytes("{\"Id\":\"d2725a22-fdfb-48df-8871-54bbcb1a95b4\",\"StartDate\":null,\"EndDate\":null}"))
                ));
        }

        public static T DeserializeJsonMessage<T>(Message message) where T : IMessage
        {
            var convertedMessage = JsonConvert.DeserializeObject<T>(
                Encoding.UTF8.GetString(message.Body),
                new JsonSerializerSettings { NullValueHandling = NullValueHandling.Ignore });

            return convertedMessage;
        }
    }

    public interface IMessage
    {
        Guid Id { get; set; }
        DateTime StartDate { get; set; }
        DateTime EndDate { get; set; }
    }

    public class SampleMessage : IMessage
    {
        public Guid Id { get; set; }
        public DateTime StartDate { get; set; }
        public DateTime EndDate { get; set; }

        public SampleMessage(Guid id, DateTime startDate, DateTime endDate)
        {
            Id = id;
            StartDate = startDate;
            EndDate = endDate;
        }

        public override string ToString()
        {
            return JsonConvert.SerializeObject(this);
        }
    }
}

Upvotes: 5

Views: 5040

Answers (1)

Leszek Mazur
Leszek Mazur

Reputation: 2531

Did you try to set Start/End Date as nullable object and implement a Interface by them?

public class SampleMessage : IMessage
{
    public Guid Id { get; set; }
    public DateTime? StartDate { get; set; }
    public DateTime? EndDate { get; set; }

    public SampleMessage(Guid id, DateTime? startDate, DateTime? endDate)
    {
        Id = id;
        StartDate = startDate;
        EndDate = endDate;
    }

    public override string ToString()
    {
        return JsonConvert.SerializeObject(this);
    }

    DateTime IMessage.StartDate { get => this.StartDate ?? DateTime.Now; set => this.StartDate = value; }
    DateTime IMessage.EndDate { get => this.EndDate ?? DateTime.Now; set => this.EndDate = value; }
}

Upvotes: 3

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