How to open & read file in C#

I am posting here sample code, how to open a file in C# and read upto last line depends upon condition:

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Text;
using System.Windows.Forms;
using System.Data.Odbc;

FileStream fileStream = new FileStream(@"c:\file.txt", FileMode.Open);
try
{
 // read from file or write to file
}
finally
{
 fileStream.Close();
}