ใช้ c# 2015 windows app ต้องการลบข้อมูลใน gridview เช่นผมใช้ mouse selected 3 แถว ก็ต้องการลบ 3 แถว

  private void bt1_Click(object sender, EventArgs e)
        {
             try
            {
                cn.Open();
                SqlCommand cm = cn.CreateCommand();
                cm.CommandType = CommandType.Text;
                cm.CommandText = "update Detail set mg='" + label1.Text + "' where ID='" + x1 + "'";
                //cm.CommandText = "update Detail set Faction='" + tb4.Text + "' where ID='" + x1 +"'";
                cm.ExecuteNonQuery();
                cn.Close();
                loaddgv1();
                dgv1.ClearSelection();
                MessageBox.Show("Record is updated successfully", "Result", MessageBoxButtons.OK, MessageBoxIcon.Information);
                foreach (DataGridViewRow row in dgv1.Rows)
                {
                    if (row.Cells[0].Value.ToString().Equals(x1))
                    {
                        dgv1.Rows[row.Index].Selected = true;
                    }
                }
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.Message);
                cn.Close();
            }
        }