Vb.net Billing Software Source Code [work] Access

I'll provide you with a comprehensive guide and source code for a basic billing software system in VB.NET with SQL Server database.

1. Database Connection (Using SqlConnection)

Create a module mod_DB.vb to centralize your connection string:

Imports System.Data.SqlClient
Module mod_DB
Public connString As String = "Data Source=localhost\SQLEXPRESS;Initial Catalog=BillingDB;Integrated Security=True"
Public Function getConnection() As SqlConnection
    Return New SqlConnection(connString)
End Function
Public Function ExecuteNonQuery(ByVal query As String) As Integer
    Using conn As SqlConnection = getConnection()
        conn.Open()
        Using cmd As New SqlCommand(query, conn)
            Return cmd.ExecuteNonQuery()
        End Using
    End Using
End Function

End Module

Tables and Relationships

-- 1. Product table
CREATE TABLE tbl_Product (
    ProductID INT PRIMARY KEY IDENTITY(1,1),
    ProductCode NVARCHAR(50) UNIQUE,
    ProductName NVARCHAR(200),
    Unit NVARCHAR(20),
    SellingPrice DECIMAL(18,2),
    GST_Percent DECIMAL(5,2),
    StockQuantity DECIMAL(18,2)
);
-- 2. Customer table
CREATE TABLE tbl_Customer (
CustomerID INT PRIMARY KEY IDENTITY(1,1),
CustomerName NVARCHAR(150),
GSTIN NVARCHAR(15),
Address NVARCHAR(500),
Mobile NVARCHAR(15)
);
-- 3. Invoice Master table
CREATE TABLE tbl_Invoice_Master (
InvoiceNo INT PRIMARY KEY,
InvoiceDate DATETIME,
CustomerID INT FOREIGN KEY REFERENCES tbl_Customer(CustomerID),
SubTotal DECIMAL(18,2),
DiscountPercent DECIMAL(5,2),
TaxAmount DECIMAL(18,2),
GrandTotal DECIMAL(18,2)
);
-- 4. Invoice Details table
CREATE TABLE tbl_Invoice_Details (
DetailID INT PRIMARY KEY IDENTITY(1,1),
InvoiceNo INT FOREIGN KEY REFERENCES tbl_Invoice_Master(InvoiceNo),
ProductID INT FOREIGN KEY REFERENCES tbl_Product(ProductID),
Quantity DECIMAL(18,2),
Rate DECIMAL(18,2),
Amount DECIMAL(18,2)
);

This structure allows full referential integrity and easy report generation.

5. Licensing and legal considerations

• Identify license files (MIT, GPL, Apache). GPL code may require making your combined work GPL if distributed.
• Contributor provenance and patent clauses.
• Verify whether bundled libraries have compatible licenses.
• If using in commercial product, prefer permissive licenses or obtain legal review.

4. Security risks & checklist

• SQL injection via concatenated SQL statements — look for use of AddWithValue or parameterized SqlCommand.
• Hard-coded credentials or API keys in source or config files.
• Weak password storage (plain text or reversible encryption).
• Inadequate input validation (client-side only).
• Insecure file handling (path traversal when exporting invoices).
• Insecure direct object references (exposing internal IDs).
• Missing authorization checks on sensitive operations (invoice modification, refunds).
• Outdated third-party libraries with known vulnerabilities.

Action items: scan for parameterized queries, secret strings, password hashing (bcrypt/scrypt/PBKDF2), validate inputs server-side, audit libraries.

8. Recommendations before adoption

1. Run static analysis and security scan (e.g., SonarQube, Roslyn analyzers).
2. Search the codebase for secrets and remove/rotate any found.
3. Replace raw SQL concatenation with parameterized queries or ORM.
4. Implement proper password hashing and role-based authorization.
5. Add logging, error handling, and input validation.
6. Establish licensing compliance and document third-party components.
7. Write unit tests for core billing calculations (tax, discounts, totals).
8. If long-term use is planned, refactor toward layered architecture and introduce CI/CD.

4. Generating a Printable Bill (VB.NET PrintDocument)

The final piece is printing. Using the PrintDocument component from the toolbox:

Private Sub PrintInvoice()
    Dim printDoc As New Printing.PrintDocument()
    AddHandler printDoc.PrintPage, AddressOf PrintPageHandler
    Dim printDialog1 As New PrintDialog()
    printDialog1.Document = printDoc
    If printDialog1.ShowDialog() = DialogResult.OK Then
        printDoc.Print()
    End If
End Sub
Private Sub PrintPageHandler(sender As Object, e As Printing.PrintPageEventArgs)
Dim yPos As Single = e.MarginBounds.Top
Dim leftMargin As Single = e.MarginBounds.Left
Dim font As New Font("Arial", 12)
Dim largeFont As New Font("Arial", 16, FontStyle.Bold) vb.net billing software source code
'Header
e.Graphics.DrawString("ABC Electronics", largeFont, Brushes.Black, leftMargin, yPos)
yPos += 30
e.Graphics.DrawString("Invoice #: " & lblInvoiceNo.Text, font, Brushes.Black, leftMargin, yPos)
yPos += 20
e.Graphics.DrawString("Date: " & DateTime.Now.ToShortDateString(), font, Brushes.Black, leftMargin, yPos)
yPos += 30
e.Graphics.DrawString("Items:", font, Brushes.Black, leftMargin, yPos)
yPos += 20
'Loop through DataGridView rows and print them
For Each row As DataGridViewRow In dgvCart.Rows
    Dim line As String = row.Cells("ProductName").Value & " x " & row.Cells("Quantity").Value & " = " & row.Cells("Total").Value
    e.Graphics.DrawString(line, font, Brushes.Black, leftMargin, yPos)
    yPos += 20
Next
'Total
yPos += 20
e.Graphics.DrawString("Grand Total: " & lblGrandTotal.Text, New Font("Arial", 14, FontStyle.Bold), Brushes.Black, leftMargin, yPos)

End Sub

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