How can I ensure NodaTime objects always get 'stringified' to ISO formats? - nodatime

Question

When we use the NodaTime objects, it's a bit too easy to get the wrong format.
For example, we use string interpolation to construct uri's, but we really want the yyyy-MM-dd format. Same goes for logging, we don't really want any other format.
LocalDate date = new LocalDate(2020, 8, 10);
string toString = $"{date}"; // "den 10 augusti 2020"
logger.LogInformation("Date: {Date}", date); // "Date: Monday, 10 August 2020"
The documentation for ToString (which is used for the 2nd line above) states:
"The value of the current instance in the default format pattern ("D"), using
the current thread's culture to obtain a format provider."
If I change the current culture to InvariantCulture, I now get both of the above lines to show "Monday, 10 August 2020", which is better because they are consistent but neither is the yyyy-MM-dd format.
System.Threading.Thread.CurrentThread.CurrentCulture = System.Globalization.CultureInfo.InvariantCulture;
Ideally though, I would want to only customize how NodaTime objects are "stringified" to avoid any other undesired side effects of changing culture. Is there any help to get here or am I stuck?
edit:
I made a console application to have a minimal reproducible example
Console.WriteLine(new LocalDate(2020,8,13));
Console.WriteLine(ZonedDateTime.FromDateTimeOffset(DateTimeOffset.Now));
Console.WriteLine(DateTime.Now);
Console.WriteLine(DateTimeOffset.Now);
and with that I got the following output:
den 13 augusti 2020
2020-08-13T08:39:16 UTC+02 (+02)
2020-08-13 08:39:16
2020-08-13 08:39:16 +02:00
I would have liked if LocalDate had a default output of 2020-08-13 which is more useful in logs as well as string interpolation, for example: var uri = $"api/orders?date={localDate}"

Answer 1

The simplest way of achieving this is to use a CultureInfo that defaults to ISO-8601 formatting. It's reasonably easy to create that, starting with the invariant culture:
using NodaTime;
using System;
using System.Globalization;
using System.Threading;
class Program
{
static void Main(string[] args)
{
var isoCulture = (CultureInfo) CultureInfo.InvariantCulture.Clone();
var format = isoCulture.DateTimeFormat;
format.ShortDatePattern = "yyyy-MM-dd";
format.ShortTimePattern = "HH:mm:ss";
format.LongTimePattern = "HH:mm:ss.FFFFFFF";
format.FullDateTimePattern = "yyyy-MM-dd'T'HH:mm:ss.FFFFFFF";
format.LongDatePattern = format.ShortDatePattern;
Thread.CurrentThread.CurrentCulture = isoCulture;
Console.WriteLine(new LocalDate(2020, 8, 13));
Console.WriteLine(ZonedDateTime.FromDateTimeOffset(DateTimeOffset.Now));
Console.WriteLine(DateTime.Now);
Console.WriteLine(DateTimeOffset.Now);
}
}
Output:
2020-08-13
2020-08-13T09:52:18 UTC+01 (+01)
2020-08-13 09:52:18.7351962
2020-08-13 09:52:18.7356716 +01:00
I believe .NET just uses "date pattern" {space} "time pattern" when formatting a DateTime, so I don't think there's a way of getting a T in there. But hey, the LocalDate output is what you wanted :)