系列4：文件操作以及读写文件

1。文件或者目录操作可以用到FileInfo,File,DirectoryInfo,Directory类：

FileInfo和File的主要区别是File的多数方法都是静态方法，DirectoryInfo与Directory区别与此相似。

2。流：In the world of I/O
manipulation, a stream represents a chunk of data. Streams provide a common way to interact with
a sequence of bytes, regardless of what kind of device (file, network connection, printer, etc.) is storing
or displaying the bytes in question.

在实际操作中，我们很少直接使用FileStream，因为它只接受直接数组类型的数据。取而代之的我们使用StreamReader, and StreamWriter这对对FileStream更好的包装。

3。Reader 和 Writer对：

Using the StringWriter and StringReader types, you can treat textual information as a stream of
in-memory characters. This can prove helpful when you wish to append character-based information
to an underlying buffer.

 4代码例子：

using System;
using System.IO;

namespace StreamWriterReaderApp
{
    public class MyStreamWriterReader
    {
        static void Main(string[] args)
        {
            Console.WriteLine("***** Fun with StreamWriter / StreamReader *****\n");

            // Get a StreamWriter and write string data.
            // StreamWriter writer = File.CreateText("Thoughts.txt");
            StreamWriter writer = new StreamWriter("reminders.txt");
            writer.WriteLine("Don't forget Mother's Day this year");
            writer.WriteLine("Don't forget Father's Day this year");
            writer.WriteLine("Don't forget these numbers:");            
            for(int i = 0; i < 10; i++)
                writer.Write(i + " ");

            // Insert a new line.
            writer.Write(writer.NewLine);

            // Closing automatically flushes!
            writer.Close();
            Console.WriteLine("Created file and wrote some thoughts");

            // Now read data from file.
            Console.WriteLine("Here are your thoughts:\n");
            // StreamReader sr = File.OpenText("reminders.txt");
            StreamReader sr = new StreamReader("reminders.txt");

            string input = null;
            while ((input = sr.ReadLine()) != null)
            {
                Console.WriteLine (input);
            }
        }
    }
}