private void btnAdd_Click(object sender, EventArgs e)
        {
            frmAddModifyProduct addProductForm = new frmAddModifyProduct();  //instantiate new Add form
            addProductForm.addProduct = true; //set bool to true that we are adding a product
            //this is used to differentiate adding and modifying (form heading)

            DialogResult result = addProductForm.ShowDialog();
            if (result == DialogResult.OK)
            {
                product = addProductForm.product; //grab the object from the Add/Modify Product form
               // txtProductCode.Text = product.ProductCode.ToString();
                this.DisplayProduct(); // populate textboxes with data from the newly created product
            }
        }
        private void btnModify_Click(object sender, EventArgs e)
        {
            frmAddModifyProduct modProductForm = new frmAddModifyProduct();  //instantiate new Add form
            modProductForm.addProduct = false; //set bool to false that we are NOT adding a product, but modifying
            //this is used to differentiate adding and modifying (form heading)

            modProductForm.product = product; // populates modify form with the product info
            DialogResult result = modProductForm.ShowDialog();
            if (result == DialogResult.OK)
            {
                product = modProductForm.product;
                this.DisplayProduct();
            }
            else if (result == DialogResult.Retry)
            {
                this.GetProduct(product.ProductCode);
                if (product != null)
                    this.DisplayProduct();
                else
                    this.ClearControls();
            }
        }