C# ASP.NET WebApi (2/Core 3.1) 大数的 Json 序列化问题

Question

I have an issue with big numbers (Int64/UInt64) being rounded by ASP.NET Json serialization. This happens in ASP.NET WebApi2 (.NET 4.5.2) as well as in ASP.NET Core WebApi (Core 3.1).

This my DTO-class:

public class TestDTO
{
    public IEnumerable<long> BigNumbers { get; set; }
}

This is my controller method:

[HttpGet]
public IHttpActionResult GetNumberTest()
{
    TestDTO dto = new TestDTO
    {
        BigNumbers = new long[]
        {
            121720000000004554,
            21720000000004554,
            1720000000004554,
            720000000004554,
        }
    };

    return Ok(dto);
}

And this is the result:

{
  "bigNumbers": [
    121720000000004560,
    21720000000004550,
    1720000000004554,
    720000000004554
  ]
}

As you can see the first two numbers are rounded (first one being rounded up, second one down), the last two are not rounded. This, of course, can be fatal behaviour. How can I disable this behaviour?

The strange thing is... when I serialize the DTO manually via Newtonsoft.Json (JsonConvert.SerializeObject), then the result is correct.

I know it works when I serialize the numbers as strings, but that´s not a real solution to the problem in my opinion. I should be able to rely on a correct serialization of my DTO.

Can anyone help me please?

Answer 1

As it turns out, the serialized raw data is correct. It´s just the visualization of SwaggerUi / Firefox through JavaScript which causes the issue.