StopwatchExt

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