How do I browse and read a text file into a TextBox?

 
using System.Text; 
using System.IO; 
private void button1_Click(object sender, System.EventArgs e) 
{ 
  OpenFileDialog ofd = new OpenFileDialog(); 
  ofd.Title = "Open the text file you wish" ; 
  ofd.InitialDirectory = "c:\" ; 
  ofd.Filter = "txt files (*.txt)|*.txt|All files (*.*)|*.*" ; 
 
 if(ofd.ShowDialog() == DialogResult.OK) 
   { 
    StreamReader sr = File.OpenText(ofd.FileName); 
    string s = sr.ReadLine(); 
    StringBuilder sb = new StringBuilder(); 
    while (s != null) 
      { 
       sb.Append(s); 
       s = sr.ReadLine(); 
      } 
      sr.Close(); 
      textBox1.Text = sb.ToString(); 
   } 
}