操作文件必须引入using System.IO;命名空间

      //获取一个文件的大小         System.IO.FileInfo file = new System.IO.FileInfo("C:\\t.txt");         int fileSize = (int)file.Length / 1024;//把文件大小换算成KB         Response.Write("<script>alert(" + fileSize.ToString() + ");</script>");

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-------创建文件夹using System.IO; private void button2_Click(object sender, EventArgs e)     {         if (Directory.Exists("\\picture"))//判断一个文件夹是否存在         {             MessageBox.Show("directory exists");         }         else {

　　　　//创建一个文件夹             Directory.CreateDirectory("\\picture");         }     }

Directory.Delete(path,true);//删除一个文件夹，其中path是文件夹的绝对路径

---------------------打开一个文件

Process.Start("C:\\t.txt");//打开一个文件

public void Page_Load(Object src,EventArgs e)   {       StreamWriter rw = File.CreateText(Server.MapPath(".")+"[url=file://mytext.txt/]\\myText.txt[/url]");       rw.WriteLine("追逐理想");       rw.WriteLine("kzlll");       rw.WriteLine(".NET笔记");       rw.Flush();       rw.Close();   } 打开文本文件 StreamReader sr = File.OpenText(Server.MapPath(".")+"[url=file://mytext.txt/]\\myText.txt[/url]");   StringBuilder output = new StringBuilder();   string rl;   while((rl=sr.ReadLine())!=null)   {   output.Append(rl+"<br>");   }   lblFile.Text = output.ToString();   sr.Close();  

C#追加文件 StreamWriter sw = File.AppendText(Server.MapPath(".")+"[url=file://mytext.txt/]\\myText.txt[/url]");      sw.WriteLine("追逐理想");        sw.WriteLine("kzlll");        sw.WriteLine(".NET笔记");        sw.Flush();        sw.Close();   C#拷贝文件          string OrignFile,NewFile;            OrignFile = Server.MapPath(".")+"[url=file://mytext.txt/]\\myText.txt[/url]";            NewFile = Server.MapPath(".")+"[url=file://mytextcopy.txt/]\\myTextCopy.txt[/url]";            File.Copy(OrignFile,NewFile,true);   C#删除文件          string delFile = Server.MapPath(".")+"[url=file://mytextcopy.txt/]\\myTextCopy.txt[/url]";            File.Delete(delFile);   C#移动文件        string OrignFile,NewFile;          OrignFile = Server.MapPath(".")+"[url=file://mytext.txt/]\\myText.txt[/url]";          NewFile = Server.MapPath(".")+"[url=file://mytextcopy.txt/]\\myTextCopy.txt[/url]";          File.Move(OrignFile,NewFile);   C#创建目录              // 创建目录c:\sixAge              DirectoryInfo d=Directory.CreateDirectory("c:\\sixAge");              // d1指向c:\sixAge\sixAge1              DirectoryInfo d1=d.CreateSubdirectory("sixAge1");              // d2指向c:\sixAge\sixAge1\sixAge1_1              DirectoryInfo d2=d1.CreateSubdirectory("sixAge1_1");              // 将当前目录设为c:\sixAge              Directory.SetCurrentDirectory("c:\\sixAge");              // 创建目录c:\sixAge\sixAge2              Directory.CreateDirectory("sixAge2");              // 创建目录c:\sixAge\sixAge2\sixAge2_1              Directory.CreateDirectory("sixAge2\\sixAge2_1");