finally fixed it...

Code:
private void generate(object sender, EventArgs e)
        {
            String dateString = yyyy.Text + dd.Text + MM.Text + hh.Text + Mi.Text + ss.Text;
            DateTime timestamp;
            if (!DateTime.TryParseExact(dateString, "yyyyddMMHHmmss", null,
                                       DateTimeStyles.None, out timestamp ))
            return; 
            long ticks = timestamp.Ticks;
            long microseconds = ticks / 10;
            convertedText.Text = microseconds.ToString("X");
        }