// Save button for the products tab
        private void btnSaveProduct_Click(object sender, EventArgs e)
        {
            string selectedProd = lstProductList.GetItemText(lstProductList.SelectedItem);
            string editedProd   = txtModifyProduct.Text;

            // Validation to see if the typed product is already in the list
            int index = lstProductList.FindString(editedProd, -1);

            if (editedProd != "" && index != -1)
            {
                MessageBox.Show("Warning: Product already exists.", "Duplicate Error", MessageBoxButtons.OK, MessageBoxIcon.Warning);
            }
            else
            {
                // Test for saving
                if (lstProductList.Enabled == false && editedProd != "") // Test if adding product
                {
                    DialogResult result = MessageBox.Show("Save '" + editedProd + "' as a new product?", "Confirm Add",
                                                          MessageBoxButtons.OKCancel, MessageBoxIcon.Exclamation);
                    if (result == DialogResult.OK)
                    {
                        ProductDB.AddProductName(editedProd);
                        this.frmModifyProductSupplier_Load(this, null);

                        // Select the item that was just saved
                        SelectItem(editedProd, lstProductList);
                    }
                }
                else if (lstProductList.Enabled == false && editedProd == "")   // If adding product, check if textbox is empty
                {
                    MessageBox.Show("Please enter a new product name.", "Entry Error",
                                    MessageBoxButtons.OK, MessageBoxIcon.Exclamation);
                    txtModifyProduct.Focus();
                }
                else if (lstProductList.Enabled == true && selectedProd != editedProd) // Test if editing a selected product
                {
                    DialogResult update =
                        MessageBox.Show("Change '" + selectedProd + "' to '" + editedProd + "'?"
                                        , "Confirm Change", MessageBoxButtons.OKCancel, MessageBoxIcon.Question);
                    if (update == DialogResult.OK)
                    {
                        ProductDB.UpdateProduct(selectedProd, editedProd);
                        // Refresh table adapter to display updated list
                        this.frmModifyProductSupplier_Load(this, null);

                        // Select the item that was just updated
                        SelectItem(editedProd, lstProductList);
                    }
                }
                else if (lstProductList.Enabled == true && selectedProd == "") // Test if editing a product but nothing is selected
                {
                    MessageBox.Show("Please select a product to edit.", "Item Not Selected",
                                    MessageBoxButtons.OK, MessageBoxIcon.Exclamation);
                    txtModifyProduct.Focus();
                }
            }
        }