private void submitButton_Click(object sender, EventArgs e)
        {
            int productId = Convert.ToInt32(productComboBox.SelectedValue.ToString());

            product.Name = productComboBox.Text;

            int totRows = dataTable.Rows.Count;

            if (totRows == 0)
            {
                MessageBox.Show("Please, before submit Click to add product Item");
                return;
            }

            foreach (DataRow dr in dataTable.Rows)
            {
                if (i == 0)
                {
                    countRecord = _purchaseManager.CountRecord();
                    i++;
                }
                randNumber       = "2019-000" + ++countRecord;
                codeTextBox.Text = randNumber;


                purchaseDetails.BillNo           = billTextBox.Text;
                purchaseDetails.CategoryId       = Convert.ToInt32(categoryComboBox.SelectedValue.ToString());
                purchaseDetails.ProductId        = Convert.ToInt32(productComboBox.SelectedValue.ToString());
                purchaseDetails.Code             = codeTextBox.Text;
                purchaseDetails.Category         = categoryComboBox.Text;
                purchaseDetails.Product          = dr["Product"].ToString();
                purchaseDetails.ManufacturedDate = menufactureDateTimePicker1.Value.ToString();
                purchaseDetails.ExpireDate       = eDateTimePicker2.Value.ToString();
                purchaseDetails.Quantity         = Convert.ToDouble(quantityTextBox.Text);
                purchaseDetails.UnitPrice        = Convert.ToDouble(unitPriceTextBox.Text);
                purchaseDetails.TotalPrice       = Convert.ToDouble(totalPriceTextBox.Text);
                purchaseDetails.MRP     = Convert.ToDouble(MRPTextBox.Text);
                purchaseDetails.Remarks = remarksTextBox.Text;

                bool isAddPurchaseItem = _purchaseManager.AddPurchaseItem(purchaseDetails);

                //_purchaseManager.DeleteProduct(productId);
            }

            //product.Name = "--Select--";
            //List<Product> loadProducts = _purchaseManager.LoadProduct();
            //loadProducts.Insert(0, product);
            //productComboBox.DataSource = loadProducts;

            //int countProducts = _purchaseManager.CountProduct(product.Name);
            //aQuantityTextBox.Text = countProducts.ToString();

            dataTable.Clear();
            purchaseDataGridView.DataSource = dataTable;
            MessageBox.Show("Iserted Successfully..");
        }