form1.cs

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

namespace WindowsFormsApplication2
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void textBox2_TextChanged(object sender, EventArgs e)
        {

        }

        private void button1_Click(object sender, EventArgs e)
        {


            OpenFileDialog dlg = new OpenFileDialog();
            dlg.Filter = "txt files (*.txt)|*.txt|All files (*.*)|*.*";
            if (dlg.ShowDialog() == DialogResult.OK)
            {
                textBox1.Text=dlg.FileName;

            }
            
            Textreader tr = new StreamReader(dlg.FileName);

            while ((string line = tr.ReadLine()) != null) { textBox2 += line; textBox2 += "/n"; }
            tr.Close();

        }

        private void textBox1_TextChanged(object sender, EventArgs e)
        {

        }
    }
}