//store the selected row index.

        private int selectedRowIndex = 0;

        public Form1() {

            InitializeComponent();

        }

        //Initialize the Data.

        private void Form1_Load(object sender, EventArgs e) {

            string strConnection = @"Data Source=.\SQLExpress;Initial Catalog=DB_Person;Integrated Security=True";

            using(SqlConnection connect = new SqlConnection(strConnection)) {

                SqlCommand cmd = connect.CreateCommand();

                cmd.CommandText = "select * from [T_Employee]";

                DataSet set = new DataSet();

                SqlDataAdapter adapter = new SqlDataAdapter(cmd);

                adapter.Fill(set, "T_Employee");

                dataGV.DataSource = set.Tables["T_Employee"];   //specify the DataSource.

                dataGV.ReadOnly = true; //read only not work when trying to delete or add rows.

                //can not add or delete rows.

                dataGV.AllowUserToAddRows = false;

                dataGV.AllowUserToDeleteRows = false;

            }

        }

        //Try to delete the DataGridView row.

        private void btn_DeleteRow_Click(object sender, EventArgs e) {