C# interactive producing incorrect results

[vsfeedback]

This issue has been moved from a ticket on Developer Community.

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[severity:I'm unable to use this version]
The following expression incorrectly returns "0" when evaluated in C# interactive:
TimeSpan.FromSeconds(0.00005). Ticks

It should return 500, as it does when called in a normal .NET process.

If my calculator started producing the wrong values I would throw it in the trash. I don't want to throw C# interactive in the trash.

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Original Comments

Feedback Bot on 2/4/2021, 10:16 PM:

We have directed your feedback to the appropriate engineering team for further evaluation. The team will review the feedback and notify you about the next steps.

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Original Solutions

(no solutions)

[MarkPflug]

TimeSpan.FromSeconds(0.0005).Ticks
produces 10000, should be 5000
TimeSpan.FromSeconds(0.005).Ticks
Correctly produces 50000

Wish I could see a pattern, but I don't.

[ufcpp]

Seems like this is a problem of .NET Framework.

using System;

Console.WriteLine(TimeSpan.FromSeconds(0.000005).Ticks);
Console.WriteLine(TimeSpan.FromSeconds(0.00005).Ticks);
Console.WriteLine(TimeSpan.FromSeconds(0.0005).Ticks);

The result is

0
0
10000

in net48 and

50
500
5000

in net5.0.

In C# Interactive, you can use .NET Core by using #reset core directive.

> #reset core
Resetting execution engine.
> TimeSpan.FromSeconds(0.00005).Ticks
500

[ufcpp]

https://docs.microsoft.com/en-us/dotnet/api/system.timespan.fromseconds?view=net-5.0

According to the document saying "the specification is accurate to the nearest millisecond", this is by design and the result in .NET 5 is rather incorrect.

[ufcpp]

see: dotnet/runtime#13230 (comment)

[MarkPflug]

Sounds like this is dotnet/runtime issue then. Hope they choose to update the docs and not revert the change in behavior. I can think of no reason that API shouldn't offer resolution down to the tick for situations like this. Rounding to the millisecond would make it less useful.

Anyway, good to know the scope of the issue and that I can continue to depend on the interactive window. Thanks for investigating and thanks for the pointer about "#reset core", wasn't aware of that feature.

[CyrusNajmabadi]

Closing out as this is not an issue with interactive and the underlying cause is known and already tracked with the right team.