C#如何获取文件全路径、目录、扩展名、文件名称

using System;
using System.IO;
class Program
{
    static void Main(string[] args)
    {
        //获取当前运行程序的目录
        string fileDir = Environment.CurrentDirectory;
        Console.WriteLine("当前程序目录：" + fileDir);
        //一个文件目录
        string filePath = "C:\\JiYF\\BenXH\\BenXHCMS.xml";
        Console.WriteLine("该文件的目录：" + filePath);
        string str = "获取文件的全路径：" + Path.GetFullPath(filePath);   //-->C:\JiYF\BenXH\BenXHCMS.xml
        Console.WriteLine(str);
        str = "获取文件所在的目录：" + Path.GetDirectoryName(filePath); //-->C:\JiYF\BenXH
        Console.WriteLine(str);
        str = "获取文件的名称含有后缀：" + Path.GetFileName(filePath);  //-->BenXHCMS.xml
        Console.WriteLine(str);
        str = "获取文件的名称没有后缀：" + Path.GetFileNameWithoutExtension(filePath); //-->BenXHCMS
        Console.WriteLine(str);
        str = "获取路径的后缀扩展名称：" + Path.GetExtension(filePath); //-->.xml
        Console.WriteLine(str);
        str = "获取路径的根目录：" + Path.GetPathRoot(filePath); //-->C:\
        Console.WriteLine(str);
        Console.ReadKey();
    }
}

using System;
using System.IO;
using Microsoft.VisualBasic.Devices;
namespace ChangeSuffix
{
    class Program
    {
        static public string path = @"E:\files";
        static void Main(string[] args)
        {
            Computer myComputer = new Computer();
            DirectoryInfo dir = new DirectoryInfo(path);
            FileInfo[] files = dir.GetFiles();
            foreach (var file in files)
            {
                string newName = file.Name.Replace(".xlsx", ".txt");      //.xlsx修改成.txt
                if(newName != file.Name)
                    myComputer.FileSystem.RenameFile(file.FullName, newName);
            }
            Console.ReadLine();
        }
    }
}