how can i update and delete a row in gridview

protected void GridView1_RowUpdating(object sender, GridViewUpdateEventArgs e)
    {
            GridViewRow row = GridView1.Rows[e.RowIndex];
            string constr = ConfigurationManager.ConnectionStrings["connstr"].ToString();
            SqlConnection con = new SqlConnection(constr);

            string id = (((Label)row.FindControl("lblid")).Text).ToString();

            string comments = (((TextBox)row.FindControl("txtcomments")).Text).ToString();
            con.Open();
            SqlCommand CmdSql = new SqlCommand("Update leave set admin_comments='" + comments + "', granted='" + true + "' where id=" + id + " ", con);
                    CmdSql.ExecuteNonQuery();
                    GridView1.EditIndex = -1;
                    con.Close();
                    gridpop();

}

public partial class DataTrialForm : Form
    {
        private String connectionString = null;
        private SqlConnection sqlConnection = null;
        private SqlDataAdapter sqlDataAdapter = null;
        private SqlCommandBuilder sqlCommandBuilder = null;
        private DataTable dataTable = null;
        private BindingSource bindingSource = null;
        private String selectQueryString = null;

        public DataTrialForm()
        {
            InitializeComponent();
        }

        private void DataTraiForm_Load(object sender, EventArgs e)
        {
          sqlConnection = new SqlConnection("data source=SEZ-WS-137\\SQLEXPRESS2008;initial catalog=AttendanceData;user id=sa;password=pass");

            selectQueryString = "select top 20 * from Attendance  order by punchtime asc";

            sqlConnection.Open();

            sqlDataAdapter = new SqlDataAdapter(selectQueryString, sqlConnection);
            sqlCommandBuilder = new SqlCommandBuilder(sqlDataAdapter);

            dataTable = new DataTable();
            sqlDataAdapter.Fill(dataTable);

            bindingSource = new BindingSource();
            bindingSource.DataSource = dataTable;

            dataGridViewTrial.DataSource = bindingSource;

           // to hide Identity column
            dataGridViewTrial.Columns[0].Visible = false;
        }

        private void addUpadateButton_Click(object sender, EventArgs e)
        {
            try
            {
                sqlDataAdapter.Update(dataTable);
            }
            catch (Exception exceptionObj)
            {
                MessageBox.Show(exceptionObj.Message.ToString());
            }
        }

       private void deleteButton_Click(object sender, EventArgs e)
        {
            try
            {
               dataGridViewTrial.Rows.RemoveAt(dataGridViewTrial.CurrentRow.Index);
               sqlDataAdapter.Update(dataTable);
            }
            catch (Exception exceptionObj)
            {
               MessageBox.Show(exceptionObj.Message.ToString());
            }
        }
    }