Reading Text from Files (C#.net)

private void button2_Click(object sender, EventArgs e)
{
try
{
 string buffer;
 StringBuilder stb = new StringBuilder();
 StreamReader strmRdr = File.OpenText("c:\\testfile.txt");
 while ((buffer = strmRdr.ReadLine()) != null)
 {
  stb.Append(buffer);
  stb.Append(Environment.NewLine);