Program.cs

using System;
using System.Numerics;
using System.Globalization;
using System.Text;
using System.Diagnostics;
using System.Threading;


namespace StringPaddingTest
{
	class MainClass
	{
		static BigInteger b = ulong.MaxValue;
		static BigInteger b2 = BigInteger.Multiply (b, 1000000000000000000);

		public static void Main (string[] args)
		{
			TestOld ();
			TestNew ();
			TestOld ();
			TestNew ();
			TestOld ();
			TestNew ();
		}

		static void TestOriginal ()
		{
			var s = new Stopwatch ();
			s.Start ();
			for (int x = 0; x < 100000; x++) {
				b.ToLexicographicId ();
				b2.ToLexicographicId ();
			}
			s.Stop ();
			Console.WriteLine ("Original time: {0}", s.ElapsedMilliseconds);
		}

		static void TestSimple ()
		{
			var s = new Stopwatch ();
			s.Start ();
			for (int x = 0; x < 100000; x++) {
				b.ToLexyId ();
				b2.ToLexyId ();
			}
			s.Stop ();
			Console.WriteLine ("Simple time: {0}", s.ElapsedMilliseconds);
		}
	}

	public static class IdExtensions
	{
		// Most NoSQL storage technologies order records by a single Id field
		// that is lexicographically sorted. This will cause flake-ids to be
		// incorrectly sorted. In order to handle this, this extension class
		// provides the ability to front-pad an id with 0s so that it will sort
		// correctly in a lexicographic system.

		//Maximum 128 bit integer:               340282366920938463463374607431768211455
		//                                       0        1         2         3
		//                                       123456789012345678901234567890123456789
		public static readonly string PADDING = "000000000000000000000000000000000000000";
		public static string ToLexicographicId(this BigInteger id)
		{
			var stringId = id.ToString();
			var padding = PADDING.ToCharArray();
			stringId.CopyTo(0, padding, 39 - stringId.Length, stringId.Length);
			return new string(padding);
		}
	}

	public static class IdExtensions2
	{
		public static string ToLexyId(this BigInteger id)
		{
			return id.ToString().PadLeft (39, '0');
		}
	}
}