生成随机数

char[] constant = { 'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z' };
Random r = new Random(System.Environment.TickCount);
string sb;
sb = DateTime.Now.ToString("yyyyMMdd").ToString() + System.Environment.TickCount.ToString() + constant[r.Next(26)] + r.Next(100, 999).ToString();