gistfile1.cs

        [Test]
        public void RegexTest()
        {
            var pattern = @"^(CONNECT|DELETE|HEAD|GET|OPTIONS|POST|PUT|TRACE) (\/[\S]*) HTTP\/(1.0|1.1)$";

            var line = "test";
            var stopWatch = Stopwatch.StartNew();
            for (int i = 0; i < 2; i++)
            {
                stopWatch.Restart();
                var m = Regex.Match(line, pattern, RegexOptions.Compiled);
                Console.WriteLine("Regex.Match: " + stopWatch.GetTimeString());
            }

            var regex = new Regex(pattern, RegexOptions.Compiled);
            stopWatch.Restart();
            var n = regex.Match(line);
            Console.WriteLine("regex.Match: " + stopWatch.GetTimeString());
        }

gistfile2.txt

Outputs:
Regex.Match: 182,2 ms
Regex.Match: 1,9 ms
regex.Match: 1,6 µs

gistfile3.cs

    public static class StopwatchExt
    {
        public static string GetTimeString(this Stopwatch stopwatch, int numberofDigits = 1)
        {
            double time = stopwatch.ElapsedTicks / (double)Stopwatch.Frequency;
            if (time > 1)
                return Math.Round(time, numberofDigits) + " s";
            if (time > 1e-3)
                return Math.Round(1e3 * time, numberofDigits) + " ms";
            if (time > 1e-6)
                return Math.Round(1e6 * time, numberofDigits) + " µs";
            if (time > 1e-9)
                return Math.Round(1e9 * time, numberofDigits) + " ns";
            return stopwatch.ElapsedTicks + " ticks";
            throw new NotImplementedException("message");
        }
    }