Array List Counter in asp.net c#

        string branch="CSE";

    

        string semester = "7";

        string cs = ConfigurationManager.AppSettings["keyname"];

        cn = new SqlConnection(cs);

        cn.Open();

        ArrayList myarray = new ArrayList();

     string k = "SELECT  email  FROM table where year='" + ListBox1.Text  + "' GROUP BY email";

        cm = new SqlCommand(k, cn);

        dr = cm.ExecuteReader();

        while (dr.Read())

        {

            myarray.Add(dr["email"]);

        }

        Label120.Text = myarray.Count.ToString();

    }