TextBox AutoSuggest from database in c#

private void DocNamePopUp()

        {

            AutoCompleteStringCollection DataCollection = new AutoCompleteStringCollection();

            getData(DataCollection);

            txtDocName.AutoCompleteSource = AutoCompleteSource.CustomSource;

            txtDocName.AutoCompleteCustomSource = DataCollection;

        }

        private void getData(AutoCompleteStringCollection dataCollection)

        {

            string connetionString = null;

            SqlConnection connection;

            SqlCommand command;

            SqlDataAdapter adapter = new SqlDataAdapter();

            DataSet ds = new DataSet();

            using(SqlConnection connection = new SqlConnection(CS));

            try

            {

                connection.Open();

                command = new SqlCommand("spGetDoctorNames", connection);

                command.CommandType = CommandType.StoredProcedure;

                adapter.SelectCommand = command;

                adapter.Fill(ds);

                adapter.Dispose();

                command.Dispose();

                foreach (DataRow row in ds.Tables[0].Rows)

                {

                    dataCollection.Add(row[0].ToString());

                }

            }

            catch (Exception ex)

            {

                MessageBox.Show("Can not open connection ! ");

            }

        }