I Wish To Call A Specific Function On Indexchanged/Itemchanged Event Of Drop Down List ,In Fact I Tried But Its Not Working

public void searchFor_Company()
        {
            using (MySqlConnection con = new MySqlConnection(CS))
            {
                using (MySqlCommand cmd = new MySqlCommand())
                {
                    cmd.CommandText = "select AddressId from companyaddress where CompanyName='"+drp_CompName.SelectedItem.Text.Trim()+"'";
                    cmd.Connection = con;
                    con.Open();
                    MySqlDataReader dr = cmd.ExecuteReader();
                    dr.Read();
                    txt_CompanyId.Text = dr[0].ToString();
                    con.Close();
                }
            }
        }

        protected void drp_CompName_SelectedItemChanged(object sender, EventArgs e)
        {
            searchFor_Company();
        }

        protected void drp_CompName_SelectedIndexChanged(object sender, EventArgs e)
        {
            searchFor_Company();
        }