using System;

using System.Collections.Generic;

using System.Linq;

using System.Net;

public class Program

{   

    public static void Main()

    {

        var s = "2022-10-31T18:22:16.606+00:00";

        var datetime = DateTimeOffset.Parse(s);

        Console.WriteLine($"input: {s}");

        Console.WriteLine();

        Example(datetime);

        Example_no_fff(datetime); // code is doing this

    }

    public static void Example(DateTimeOffset datetime)

    {

        Console.WriteLine(datetime.ToString("yyyy-MM-ddTHH:mm:ss.fffZ"));

        Console.WriteLine();

    }

    public static void Example_no_fff(DateTimeOffset datetime)

    {

        Console.WriteLine("note: code is doing this");

        Console.WriteLine(datetime.ToString("yyyy-MM-ddTHH:mm:ssZ"));

        Console.WriteLine();

    }

}