生成随机文件名

 Random random = new Random(DateTime.Now.Millisecond);

上传后的文件名为:

  string filename=DateTime.Now.ToString("yyyyMMddhhmmss") + random.Next(10000) +你上传文件的扩张名;

eg:
 string filename = DateTime.Now.ToString("yyyyMMddhhmmss") + random.Next(10000) + System.IO.Path.GetExtension(FileUpload1.FileName);