Private Sub SaveInvoice() Using conn As SqlConnection = getConnection() conn.Open() Dim transaction As SqlTransaction = conn.BeginTransaction() Try '1. Insert into tbl_Invoice_Master Dim masterQuery As String = "INSERT INTO tbl_Invoice_Master (InvoiceDate, CustomerID, SubTotal, TaxAmount, GrandTotal) " & "VALUES (@date, @custID, @sub, @tax, @grand); SELECT SCOPE_IDENTITY();" Dim newInvoiceNo As Integer = 0 Using cmdMaster As New SqlCommand(masterQuery, conn, transaction) cmdMaster.Parameters.AddWithValue("@date", DateTime.Now) cmdMaster.Parameters.AddWithValue("@custID", GetCurrentCustomerID()) 'Function to get selected customer ID cmdMaster.Parameters.AddWithValue("@sub", lblSubTotal.Text) cmdMaster.Parameters.AddWithValue("@tax", lblTax.Text) cmdMaster.Parameters.AddWithValue("@grand", lblGrandTotal.Text) newInvoiceNo = Convert.ToInt32(cmdMaster.ExecuteScalar()) End Using '2. Insert into tbl_Invoice_Details for each row in cart Dim detailsQuery As String = "INSERT INTO tbl_Invoice_Details (InvoiceNo, ProductID, Quantity, Rate, Total) " & "VALUES (@invNo, @prodID, @qty, @rate, @total)" For Each row As DataGridViewRow In dgvCart.Rows Using cmdDetails As New SqlCommand(detailsQuery, conn, transaction) cmdDetails.Parameters.AddWithValue("@invNo", newInvoiceNo) cmdDetails.Parameters.AddWithValue("@prodID", row.Cells("ProductID").Value) cmdDetails.Parameters.AddWithValue("@qty", row.Cells("Quantity").Value) cmdDetails.Parameters.AddWithValue("@rate", row.Cells("Rate").Value) cmdDetails.Parameters.AddWithValue("@total", row.Cells("Total").Value) cmdDetails.ExecuteNonQuery() '3. Update stock in tbl_Products Dim stockQuery As String = "UPDATE tbl_Products SET StockQuantity = StockQuantity - @qty WHERE ProductID = @prodID" Using cmdStock As New SqlCommand(stockQuery, conn, transaction) cmdStock.Parameters.AddWithValue("@qty", row.Cells("Quantity").Value) cmdStock.Parameters.AddWithValue("@prodID", row.Cells("ProductID").Value) cmdStock.ExecuteNonQuery() End Using End Using Next transaction.Commit() MessageBox.Show("Invoice saved successfully. Invoice No: " & newInvoiceNo) ClearCart() Catch ex As Exception transaction.Rollback() MessageBox.Show("Failed to save invoice: " & ex.Message) End Try End Using End Sub The final piece is printing. Using the PrintDocument component from the toolbox:
Private Sub AddProductToCart(productID As Integer, qty As Integer) 'Fetch product details from database using productID Dim query As String = "SELECT ProductName, SellingPrice, GST_Percent FROM tbl_Products WHERE ProductID = " & productID Using conn As SqlConnection = getConnection() conn.Open() Using cmd As New SqlCommand(query, conn) Dim reader As SqlDataReader = cmd.ExecuteReader() If reader.Read() Then Dim productName As String = reader("ProductName").ToString() Dim price As Decimal = Convert.ToDecimal(reader("SellingPrice")) Dim gstPercent As Integer = Convert.ToInt32(reader("GST_Percent")) 'Add row to DataGridView (dgvCart) dgvCart.Rows.Add(productID, productName, qty, price, qty * price, gstPercent) CalculateTotal() 'Update subtotal, tax, grand total End If End Using End Using End Sub vb.net billing software source code
Public Function getConnection() As SqlConnection Return New SqlConnection(connString) End Function Private Sub SaveInvoice() Using conn As SqlConnection =