//文件夾路徑string strFolderPath = Server.MapPath("~") + "//excel//";DirectoryInfo dyInfo = new DirectoryInfo(strFolderPath);//獲取文件夾下所有的文件foreach (FileInfo feInfo in dyInfo.GetFiles()){  //判斷文件日期是否小于今天，是則刪除  if (feInfo.CreationTime < DateTime.Today)    feInfo.Delete();}