C#

string[] dn = usr.DistinguishedName.Split(',');
Array.Reverse(dn);

TreeNode root = new TreeNode();
TreeNode prev = new TreeNode();

foreach (string s in dn)
{
    if (s.Contains("OU="))
    {
        string tmp = s.Replace("OU=", string.Empty);

        if (string.IsNullOrEmpty(root.Text))
        {
            root.Text = tmp;
        }
        else
        {
            if (string.IsNullOrEmpty(prev.Text))
            {
                prev.Text = tmp;
                root.Nodes.Add(prev);
            }
            else
            {
                TreeNode n = new TreeNode();
                n.Text = tmp;

                prev.Nodes.Add(n);
                prev = n;
            }
        }
    }
}
tvUsers.Nodes.Add(root);

static void Main(string[] args)
{
   AppDomain currentDomain = AppDomain.CurrentDomain;
   currentDomain.UnhandledException += new UnhandledExceptionEventHandler(currentDomain_UnhandledException);

   #if !DEBUG
   try
   {
   #endif
   // If Debug Mode, run Application
   // Otherwise, setup as service
   #if DEBUG
     isDebugMode = true;
     object debug = new object();
     MessagingBroker(debug);
   #else
     ServiceBase.Run(new Program());
   #endif
  #if !DEBUG
  }
  catch (Exception e)
  {
   // Log Error to Event Viewer
   string msg = "Error: " + e.Source + "\r\n";
   msg += "Message: " + e.Message + "\r\n";
   msg += "Stack Trace: " + e.StackTrace;
   sEvent = e.Source;
   LogEvent(msg, EventLogEntryType.Error);
  }
  #endif
}

private void lnklblLogIn_LinkClicked(object sender, LinkLabelLinkClickedEventArgs e)
{
    sp.Stop();
    frmLogIn LogIn = new frmLogIn();
    LogIn.Show();                     
}

private void btnLogIn_Click(object sender, EventArgs e)
        {
            OleDbConnection con = new OleDbConnection(@"Provider=Microsoft.Jet.OLEDB.4.0;Data Source=C:\\Users\\John\\Desktop\\Database1.mdb");
            OleDbCommand com = new OleDbCommand("SELECT UserName, PassWord FROM Table1",con);
            OleDbDataReader reader;
            
            bool permit = false;

            try
            {
                con.Open();
                reader = com.ExecuteReader();
                while (reader.Read())
                {
                    if (txtUserName.Text == (reader["UserName"].ToString()) && mtxtPassWord.Text == reader["PassWord"].ToString())
                    {
                        permit = true;
                        break;
                    }
                }

                con.Close();
            }
            catch
            {
                MessageBox.Show("File not able to be read");
                return;
            }

            if (permit != true)
                MessageBox.Show("Username or Password are not correct.");
            else
            {
                Close();
            }
                
        }