Datagridview with checkbox in c#

foreach (DataGridViewRow row in dataGridView1.Rows)
            {
                if (row.Cells[1].Value != null && (bool)row.Cells[1].FormattedValue)
                {
                        DialogResult dlgRes;
                        string teststr = "Are you want to delete";
                        dlgRes = MessageBox.Show(teststr, "Confirm Document Close", MessageBoxButtons.YesNo, MessageBoxIcon.Warning);
                        if (dlgRes == DialogResult.Yes)
                        {
                            
                            int idtoselect = (int)row.Cells[0].Value;
                            String str1 = idtoselect.ToString();
                            string constr = "DELETE FROM Member Where ID_Member =" + str1 + "";
                            SqlCommand cmd = new SqlCommand(constr, conn);
                            cmd.ExecuteNonQuery();
                            ds.Tables["Member"].Clear();
                            da.Fill(ds, "Member");
                            dataGridView1.DataSource = ds.Tables["Member"];
                        }
                        else
                        {
                            ds.Tables["Member"].Clear();
                            da.Fill(ds, "Member");
                            dataGridView1.DataSource = ds.Tables["Member"];
                        }
                    }
               }