' 3. Extract processing line iterations values sequentiallyUsing conn As OleDbConnection = GetDatabaseConnection()Dim query As String = "SELECT p.ProductName, d.Quantity, d.Price, d.Total FROM InvoiceDetails d INNER JOIN Products p ON d.ProductID = p.ProductID WHERE d.InvoiceID = ?"Using cmd As New OleDbCommand(query, conn)cmd.Parameters.AddWithValue("?", ActiveInvoiceID)Using reader As OleDbDataReader = cmd.ExecuteReader()While reader.Read()Dim name As String = reader("ProductName").ToString().PadRight(20).Substring(0, 20)Dim qty As String = reader("Quantity").ToString().PadRight(8)Dim price As String = Convert.ToDecimal(reader("Price")).ToString("F2").PadRight(12)Dim total As String = Convert.ToDecimal(reader("Total")).ToString("F2")

Developing a robust billing and invoicing system is a foundational requirement for many enterprise applications. Visual Basic .NET (VB.NET) combined with Windows Forms (WinForms) and a relational database provides a reliable, rapid-development ecosystem for creating desktop-based point-of-sale (POS) and invoicing solutions.

#Region "Printing Engine Routines"Private Sub PrintInvoiceReceipt()Dim printDoc As New PrintDocument()AddHandler printDoc.PrintPage, AddressOf PrintPageHandler

Seamless connection with Excel and local printers.

-- 1. Products Table CREATE TABLE Products ( ProductID INT IDENTITY(1,1) PRIMARY KEY, ProductCode VARCHAR(50) UNIQUE NOT NULL, ProductName VARCHAR(100) NOT NULL, UnitPrice DECIMAL(18, 2) NOT NULL, StockQuantity INT NOT NULL ); -- 2. Invoice Master Table CREATE TABLE Invoices ( InvoiceID INT IDENTITY(1,1) PRIMARY KEY, InvoiceNumber VARCHAR(50) UNIQUE NOT NULL, InvoiceDate DATETIME DEFAULT GETDATE(), CustomerName VARCHAR(100) NOT NULL, SubTotal DECIMAL(18, 2) NOT NULL, TaxAmount DECIMAL(18, 2) NOT NULL, Discount DECIMAL(18, 2) NOT NULL, GrandTotal DECIMAL(18, 2) NOT NULL ); -- 3. Invoice Items (Details) Table CREATE TABLE InvoiceItems ( ItemID INT IDENTITY(1,1) PRIMARY KEY, InvoiceID INT FOREIGN KEY REFERENCES Invoices(InvoiceID) ON DELETE CASCADE, ProductID INT FOREIGN KEY REFERENCES Products(ProductID), Quantity INT NOT NULL, UnitPrice DECIMAL(18, 2) NOT NULL, LineTotal DECIMAL(18, 2) NOT NULL ); Use code with caution. 3. Database Connection Module ( DbConnection.vb )

Most VB.NET billing systems use (Express or LocalDB) or MS Access for lighter deployments. For this guide, we will outline a SQL Server schema.

This layer contains the calculations and validation rules (e.g., checking if stock exists before adding it to an invoice). 4. The Presentation Layer (Windows Forms)

This article will serve as a deep dive into the architecture, features, database design, and actual code structure of a professional billing software built with VB.NET.

Ensures fewer runtime errors, which is critical for financial calculations.