private void btnADD_PRODUCT_Click(object sender, EventArgs e)
        {
            FrmAdd_NewProduct frm = new FrmAdd_NewProduct(idInvoice);

            frm.d += new FrmAdd_NewProduct.myDEL(Show);
            frm.Show();
        }
 // button add product for invoice
 private void btnAddProduct_Click(object sender, EventArgs e)
 {
     if (String.IsNullOrEmpty(txtID_INVOICE.Text))
     {
         MessageBox.Show("Vui lòng chọn hóa đơn cần thêm hàng hóa", "Thông báo", MessageBoxButtons.OK, MessageBoxIcon.Information);
     }
     else
     {
         FrmAdd_NewProduct frmAddNewProduct = new FrmAdd_NewProduct(idInvoice, false);
         frmAddNewProduct.d += new FrmAdd_NewProduct.myDel(LoadDGVs);
         frmAddNewProduct.Show();
     }
 }