引入了using System.IO 需要用到 FileInfo 类。 FileInfo 类用于提供创建、复制、删除、移动和打开文件的实例方法，并且帮助创建 FileStream 对象。获取文件名、文件长度、获取当前 FileSystemInfo 对象的创建时间、写入时间、访问时间。-Introduced using System.IO　need to use FileInfo class. FileInfo class is used to provide create, copy, delete, move, and open the file instance methods, and help create a FileStream object. Get the file name, file size, to get the current FileSystemInfo object creation time, write time, access time.