private void btnComplete_Click(object sender, EventArgs e) { if (cmbClerkName.SelectedIndex == -1) //check is employee name selected { MessageBox.Show("You have to choose your name before submit order."); } else if (cmbCustomerID.SelectedIndex == -1) // Check is customer selected { MessageBox.Show("You have to choose customer before submit order."); } else { if (checkStock() == null) // If no outOfStock product, update DataBase { updateDataBase(); } // Open confirmation for to dispaly result Form myfrmConfirmation = new frmConfirmation(this); myfrmConfirmation.MdiParent = this.MdiParent; myfrmConfirmation.Text = "Confirmation for " + this.Text; myfrmConfirmation.Show(); } }