Output an ISO 8601 string

Question

How do we create a date/time in a specific timezone and output a short ISO 8601 date/time with offset from UTC? For instance, 5 PM Pacific Standard Time on 08 September 2015 must look like this:

2015-09-08T17:00:00-07:00

Here is my current attempt.

using System;
using NodaTime;
using NodaTime.Text;

namespace ConsoleApplication1_Nodatime
{
    class Program
    {
        public static void Log(string x) => Console.WriteLine(x);
        public static void Read() => Console.ReadLine();

        static void Main(string[] args)
        {
            var localDateTime = new LocalDateTime(2015, 09, 08, 17, 0);
            var zone = DateTimeZoneProviders.Tzdb.GetZoneOrNull("America/Vancouver");
            var zonedDateTime = localDateTime.InZoneStrictly(zone);
            Log(zonedDateTime.ToOffsetDateTime().ToString());
            Read();
        }
    }
}

This works, though seems like too many steps.

1. Create a LocalDateTime
2. Create a DateTimeZone
3. Convert the LocalDateTime to a ZonedDateTime
4. Convert the ZonedDateTime to an OffsetDateTime

How do we do it with fewer steps?

Answer 1

As noted in the comments of the question, you only need a ZonedDateTime in order to achieve your desired formatting (no need for the OffsetDateTime). The format string passes the "general" offset pattern so that the minutes should be included ("medium format") only if the offset has minutes.

zonedDateTime.ToString(
    "yyyy-MM-ddTHH:mm:sso<g>", 
    System.Globalization.CultureInfo.InvariantCulture)

For brevity, here are the available offset patterns documented:

• f: Full format, displaying all information including fractional seconds. Typical pattern text: +HH:mm:ss.fff
• l: Long format, displaying information down to the second. Typical pattern text: +HH:mm:ss
• m: Medium format, displaying information down to the minute. Typical pattern text: +HH:mm
• s: Short format, displaying information down to the hour. Typical pattern text: +HH
• g: General pattern. Formatting depends on the value passed in:
  • If the offset has fractional seconds, the full format is used; otherwise
  • If the offset has seconds, the long format is used; otherwise
  • If the offset has minutes, the medium format is used; otherwise
  • The short format is used When parsing, the other standard format patterns are tried one at a time. This is the default format pattern.
• G: As g, but using Z for an offset of 0, as if it were Z-prefixed.

Source: http://nodatime.org/1.3.x/userguide/offset-patterns.html

ORIGINAL QUESTION

With the original request to format as ISO-8601 always showing the trailing minutes, you can use the custom format string below. By default, it meets ISO-8601 standards which does not require the trailing ":00". However, you can pass an offset pattern to force the formatting you are wanting:

zonedDateTime.ToString(
    "yyyy-MM-ddTHH:mm:sso<m>", 
    System.Globalization.CultureInfo.InvariantCulture)

Source: http://nodatime.org/1.3.x/userguide/offset-patterns.html

UPDATE TO SHORTEN CODE

If you're just looking to shorten code, you can always wrap the code in a helper method - possibly even as a static extension method.

public static class NodaTimeHelpers
{
    public static Lazy<DateTimeZone> Zone = new Lazy<DateTimeZone>(
        () => DateTimeZoneProviders.Tzdb.GetZoneOrNull("America/Vancouver"));
    public static string ToStringWithOffset(this LocalDateTime localDateTime)
    {
        if (localDateTime == null)
            return "";
        var zonedDateTime = localDateTime.InZoneStrictly(Zone.Value);
        return zonedDateTime.ToString(
            "yyyy-MM-ddTHH:mm:sso<g>",
            System.Globalization.CultureInfo.InvariantCulture);
    }
}

This allows your local date time object to convert to string very easily:

localDateTime.ToStringWithOffset();