Inconsistent behavior of JsonConvert.DeserializeObject for Decimal property value starting with 0

[liladhar-nimje]

Bug:

I have seen inconsistent behavior of JsonConvert.DeserializeObject() for the decimal property whose value starts with 0. Please find the below code in C#.

using Newtonsoft.Json;
using System;

namespace Example
{
    class Program
    {
        static void Main(string[] args)
        {
            var jsonExample1 = "{ \"amount\": 01234 }";
            var jsonExample2 = "{ \"amount\": 0800 }";

            try
            {
                // CASE #1
                var example1 = JsonConvert.DeserializeObject<Example>(jsonExample1); // Sets the Amount = 668
                Console.WriteLine(example1.Amount);

                // CASE #2
                var example2 = JsonConvert.DeserializeObject<Example>(jsonExample2); // throws an error - Input string '0800' is not a valid decimal.
                Console.WriteLine(example2.Amount);
            }
            catch (Exception ex)
            {
                Console.WriteLine(ex.Message);
            }
        }
    }

    public class Example
    {
        public decimal Amount { get; set; }
    }
}

Output:

Expected behavior

In CASE 1 => It should set the Amount = 1234 or 01234
In CASE 2 => It should set the Amount = 0800 or 800

Actual behavior

In CASE 1 => It sets the Amount = 668
In CASE 2 => It is throwing an error - "Input string '0800' is not a valid decimal."

Steps to reproduce

Create a sample console application in .Net Core and replace the program.cs code with the above code.

[bartelink]

This is known/by design, see this writeup: https://stackoverflow.com/a/37579424/11635

Also, for code blocks, don't forget to wrap them in triple backtick comments so they format correctly

[liladhar-nimje]

@bartelink - the mentioned writeup explains to me CASE 2 which means it is throwing an invalid value. But what about CASE 1, there also it should have thrown the same error, but it is not. Instead, it is calculated as some other value, that is the real concern about the issue. Is that also known /by design?

var jsonExample1 = "{ \"amount\": 01234 }";
JsonConvert.DeserializeObject<Example>(jsonExample1); // Why this sets the Amount = 668

[bartelink]

Yes, if you read on, you'll see it's being interpreted as octal (base 8). You'll also see that this is a debatable but not uncommon interpretation from the point of view of 'standard' JSON, insofar as that exists. I have not drilled in to the issue and/or the code to see whether it's still hard-wired - that's your opportunity ;)