using System;
using System.IO;

class TextFileWriter
{
static void Main(string[] args)
{
// create a writer and open the file
TextWriter tw = new StreamWriter(“date.txt”);

// write a line of text to the file
tw.WriteLine(DateTime.Now);

// close the stream
tw.Close();
}
}

using System;
using System.IO;

class TextFileReader
{
static void Main(string[] args)
{
// create reader & open file
Textreader tr = new StreamReader(“date.txt”);

// read a line of text
Console.WriteLine(tr.ReadLine());

// close the stream
tr.Close();
}
}
http://www.csharp-station.com/HowTo/ReadWriteTextFile.aspx