https://ayende.com/blog/176035/making-code-faster-the-obvious-costs

Record.cs

   public class Record
    {
        public DateTime Start;
        public DateTime End;
        public long Id;

        public TimeSpan Duration => End - Start;
        private static long[] _pows = Enumerable.Range(0, 8).Select(i => (long)Math.Pow(10, i)).ToArray();
        public Record(string line)
        {
         
            
            Start = new DateTime(
                (int) (Char.GetNumericValue(line[0])*1000+ Char.GetNumericValue(line[1])*100+ Char.GetNumericValue(line[2])*10+ Char.GetNumericValue(line[3])),
                (int)(Char.GetNumericValue(line[5]) * 10 + Char.GetNumericValue(line[6])),
                (int)(Char.GetNumericValue(line[8]) * 10 + Char.GetNumericValue(line[9])),
                (int)(Char.GetNumericValue(line[11]) * 10 + Char.GetNumericValue(line[12])),
                (int)(Char.GetNumericValue(line[14]) * 10 + Char.GetNumericValue(line[15])),
                (int)(Char.GetNumericValue(line[17]) * 10 + Char.GetNumericValue(line[18])));
            const int dateEndStartChar = 20;
            End = new DateTime(
              (int)(Char.GetNumericValue(line[0+dateEndStartChar]) * 1000 + Char.GetNumericValue(line[1 + dateEndStartChar]) * 100 + Char.GetNumericValue(line[2 + dateEndStartChar]) * 10 + Char.GetNumericValue(line[3 + dateEndStartChar])),
              (int)(Char.GetNumericValue(line[5 + dateEndStartChar]) * 10 + Char.GetNumericValue(line[6 + dateEndStartChar])),
              (int)(Char.GetNumericValue(line[8 + dateEndStartChar]) * 10 + Char.GetNumericValue(line[9 + dateEndStartChar])),
              (int)(Char.GetNumericValue(line[11 + dateEndStartChar]) * 10 + Char.GetNumericValue(line[12 + dateEndStartChar])),
              (int)(Char.GetNumericValue(line[14 + dateEndStartChar]) * 10 + Char.GetNumericValue(line[15 + dateEndStartChar])),
              (int)(Char.GetNumericValue(line[17 + dateEndStartChar]) * 10 + Char.GetNumericValue(line[18 + dateEndStartChar])));
            for (int i = 7; i >=  0; i--)
            {
                Id += (long)(char.GetNumericValue(line[i+40])* _pows[i]);
            }
        }
    }