.NET 4.x Сканер баркода - C#

DateTime _lastKeystroke = new DateTime(0);
            List<char> _barcode = new List<char>(10);
            // check timing (keystrokes within 100 ms)
            TimeSpan elapsed = (DateTime.Now - _lastKeystroke);
            if (elapsed.TotalMilliseconds > 100 && e.KeyChar >= 39)
            {
                _barcode.Clear();
                MessageBox.Show("salam");
 
            }
            // record keystroke & timestamp
            _barcode.Add(e.KeyChar);
            _lastKeystroke = DateTime.Now;
 
            // process barcode
            if (e.KeyChar == 39 && _barcode.Count > 0)
            {
                string msg = new String(_barcode.ToArray());
                MessageBox.Show(msg);
                _barcode.Clear();
            }