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();