C#：IO

1. File和Directory类

这两个类属于静态类，经常用到的比如File.Exists(string path), Directory.Exists(string path), Directory.GetCurrentDirectory(), Directory.SetCurrentDirectory(string path);

另外还有FileInfo和DirectoryInfo类，属于实例类，用法跟File和Directory差不多，就是要先实例化出来

当单一调用的时候优先用File和Directory类，如果操作很多，则用FileInfo和DirectoryInfo类会更好

2. FileStream类

用于指向文件的流操作，读写文档没StreamReader和StreamWriter方便

当然FileStream类最牛逼的地方在于Seek(long offset, SeekOrigin)这个方法

FileStream(string fileName, FileMode);

FileStream(string fileName, FileMode, FileAccess);

     public enum FileMode
     {
         Append,
         Create,
         CreateNew,
         Open,
         OpenOrCreate,
         Truncate
     }

public enum FileMode

     public enum FileAccess
     {
         Read,
         ReadWrite,
         Write
     }

public enum FileAccess

3. FileWriter

虽然FileWriter能够直接对文件写入，但是没有更多选项，所以一般要先创建一个FileStream，再创建FileWriter

4.FileReader

与FileWriter一样，但是FileStream的FileMode要改改

Read的时候可能会有文件不存在的BUG，所以要么加上try..catch，要么先判断exists

5. Path类

静态类，主要有GetDirectoryName和GetFileName两个方法

下面这段代码集成了上面的内容

 using System;
 using System.Collections.Generic;
 using System.Linq;
 using System.Text;
 using MySql.Data;
 using MySql.Data.Entity;
 using MySql.Data.MySqlClient;
 using System.IO;

 namespace test4
 {
     class Program
     {
         const string FILE = @"C:\Users\Administrator\Desktop\test.txt";
         const string DIRECTORY = @"C:\Users\Administrator\Desktop\";
         static void Main(string[] args)
         {
             if (File.Exists(FILE))
             {
                 Console.WriteLine("test.txt exist on desktop");
             }
             if (Directory.Exists(DIRECTORY))
             {
                 Console.WriteLine("Desktop directory exists");
             }
             Console.WriteLine(Directory.GetCurrentDirectory());
             Console.WriteLine(Path.GetDirectoryName(FILE));
             Console.WriteLine(Path.GetFileName(FILE));
             //FileStream fst = File.OpenRead(FILE);
             //StreamWriter sw = new StreamWriter(FILE, true);
             FileStream fst = new FileStream(FILE, FileMode.Append | FileMode.OpenOrCreate);
             StreamWriter sw = new StreamWriter(fst);
             sw.WriteLine("xueyiyi");
             sw.Close();
             fst.Close();
             //try
             //{
             //    fst = new FileStream(FILE, FileMode.Open);
             //    StreamReader sr = new StreamReader(fst);
             //    string str;
             //    while ((str = sr.ReadLine()) != null)
             //    {
             //        Console.WriteLine(str);
             //    }
             //    sr.Close();
             //    fst.Close();
             //}
             //catch (IOException e)
             //{
             //    Console.WriteLine("An IO exception has been thrown!");
             //    Console.WriteLine(e.ToString());
             //    return;
             //}
             if (File.Exists(FILE))
             {
                 fst = new FileStream(FILE, FileMode.Open);
                 StreamReader sr = new StreamReader(fst);
                 string str;
                 while ((str = sr.ReadLine()) != null)
                 {
                     Console.WriteLine(str);
                 }
                 sr.Close();
                 fst.Close();
             }
             else
             {
                 Console.WriteLine(FILE + " does not exist");
             }
         }
     }
 }

用StreamWriter类可以简单实现文件写入

StreamWriter s = new StreamWriter(address + "/Menu.ini", true);

s.WriteLine(openFileDialog1.FileName);

s.Flush();

s.Close();

StreamReader简单实现读文件

StreamReader sr = new StreamReader(address + "/Menu.ini");

while (sr.Peek()>=0)

{

     string str = sr.ReadLine();

}

sr.Close();