In this post, we’ll break down the core components of a VB.NET billing application and provide a clear roadmap for the source code structure. Key Features of the Billing Software
Stores individual line items linked to a parent invoice (One-to-Many relationship). DetailID (AutoNumber, Primary Key) InvoiceNo (Number, Foreign Key) ProductID (Number) Quantity (Number) Price (Currency) Total (Currency) UI Design Configuration vbnet+billing+software+source+code
transaction.Commit() Return True
' Generic method to execute Non-Query (Insert, Update, Delete) Public Function ExecuteNonQuery(query As String, parameters As List(Of SqlParameter)) As Boolean Using conn As SqlConnection = GetConnection() Using cmd As New SqlCommand(query, conn) If parameters IsNot Nothing Then cmd.Parameters.AddRange(parameters.ToArray()) End If conn.Open() Dim rowsAffected As Integer = cmd.ExecuteNonQuery() Return rowsAffected > 0 End Using End Using End Function End Class In this post, we’ll break down the core components of a VB
Public Class InvoiceService Private dbHelper As New DatabaseHelper() Available: " & stock, MsgBoxStyle
Public Class frmBilling Dim db As New dbConnection() Dim subTotal As Decimal = 0.00 Dim taxRate As Decimal = 0.15 ' 15% Tax Rate Private Sub frmBilling_Load(sender As Object, e As EventArgs) Handles MyBase.Load GenerateInvoiceNumber() SetupCartGrid() End Sub ' Automatically design the DataGridView columns programmatically Private Sub SetupCartGrid() dgvCart.Columns.Clear() dgvCart.Columns.Add("ProdID", "ID") dgvCart.Columns.Add("ProdName", "Product Name") dgvCart.Columns.Add("Price", "Unit Price") dgvCart.Columns.Add("Qty", "Qty") dgvCart.Columns.Add("Total", "Total Price") dgvCart.Columns("ProdID").Visible = False End Sub ' Generate sequential invoice tracking codes Private Sub GenerateInvoiceNumber() txtInvoiceNo.Text = "INV-" & DateTime.Now.ToString("yyyyMMddHHmmss") End Sub ' Fetch and add item to cart when Product Code is validated Private Sub btnAdd_Click(sender As Object, e As EventArgs) Handles btnAdd.Click If txtProdCode.Text = "" Or txtQty.Text = "" Then MsgBox("Please enter product code and quantity.", MsgBoxStyle.Exclamation) Exit Sub End If Dim query As String = "SELECT ProductID, ProductName, Price, StockQty FROM Products WHERE ProductCode = @Code" Dim command As New SqlCommand(query, db.conn) command.Parameters.AddWithValue("@Code", txtProdCode.Text.Trim()) db.OpenConnection() Dim reader As SqlDataReader = command.ExecuteReader() If reader.Read() Then Dim stock As Integer = Convert.ToInt32(reader("StockQty")) Dim inputQty As Integer = Convert.ToInt32(txtQty.Text) ' Validate inventory threshold If inputQty > stock Then MsgBox("Insufficient stock! Available: " & stock, MsgBoxStyle.Critical) reader.Close() db.CloseConnection() Exit Sub End If Dim prodID As Integer = Convert.ToInt32(reader("ProductID")) Dim name As String = reader("ProductName").ToString() Dim price As Decimal = Convert.ToDecimal(reader("Price")) Dim total As Decimal = price * inputQty ' Add row to Cart DataGridView dgvCart.Rows.Add(prodID, name, price, inputQty, total) CalculateBillTotals() Else MsgBox("Product not found!", MsgBoxStyle.Critical) End If reader.Close() db.CloseConnection() End Sub ' Compute running totals dynamically Private Sub CalculateBillTotals() subTotal = 0 For Each row As DataGridViewRow In dgvCart.Rows If Not row.IsNewRow Then subTotal += Convert.ToDecimal(row.Cells("Total").Value) End If Next Dim taxAmount As Decimal = subTotal * taxRate Dim grandTotal As Decimal = subTotal + taxAmount lblSubTotal.Text = subTotal.ToString("N2") lblTax.Text = taxAmount.ToString("N2") lblGrandTotal.Text = grandTotal.ToString("N2") End Sub End Class Use code with caution. 5. Saving Transactions & Inventory Deduction