Open and read content of a text file

OpenFileDialog openDlg = new OpenFileDialog();
openDlg.Title = "Open a text file";
openDlg.FileName = "";
openDlg.Filter = "All Files|*.*";
string sFileName = "";
if (openDlg.ShowDialog() != DialogResult.Cancel)
{
 sFileName = openDlg.FileName;
 StreamReader sr = new StreamReader(sFileName);
 string sContent = sr.ReadToEnd();                    
 sr.Close();
 sr = null; 
}
openDlg = null;