Interactive Calculator Demo

This calculator demo showcases how to create a simple calculator application in both Visual Basic 6 and VB.NET. The calculator performs basic arithmetic operations including addition, subtraction, multiplication, and division.

Below you'll find:

A live interactive calculator you can use right now
Visual Basic 6 implementation code
Visual Basic .NET implementation code
Explanation of key concepts

Live Calculator Demo

Try the calculator below. This JavaScript implementation mimics the functionality of our VB examples.

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Visual Basic Implementation

VB6 Code

VB.NET Code

This VB6 implementation uses a form with text boxes for input, a combo box for operator selection, and a command button to perform the calculation.

Private Sub Combo1_Change()
    Call CalculateResult
End Sub

Private Sub Command1_Click()
    Call CalculateResult
End Sub

Private Sub CalculateResult()
    Dim num1 As Double
    Dim num2 As Double
    Dim result As Double
    
    ' Get values from text boxes
    If IsNumeric(Text1.Text) Then
        num1 = CDbl(Text1.Text)
    Else
        MsgBox "Please enter a valid number in the first field", vbExclamation
        Exit Sub
    End If
    
    If IsNumeric(Text2.Text) Then
        num2 = CDbl(Text2.Text)
    Else
        MsgBox "Please enter a valid number in the second field", vbExclamation
        Exit Sub
    End If
    
    ' Perform calculation based on selected operator
    Select Case Combo1.ListIndex
        Case 0 ' Addition
            result = num1 + num2
        Case 1 ' Subtraction
            result = num1 - num2
        Case 2 ' Multiplication
            result = num1 * num2
        Case 3 ' Division
            If num2 = 0 Then
                MsgBox "Cannot divide by zero", vbExclamation
                Exit Sub
            End If
            result = num1 / num2
    End Select
    
    ' Display result
    Label1.Caption = Format(result, "0.00")
End Sub

Private Sub Command2_Click()
    Unload Me
End Sub

Private Sub Form_Load()
    ' Initialize combo box with operators
    Combo1.AddItem "+"
    Combo1.AddItem "-"
    Combo1.AddItem "×"
    Combo1.AddItem "÷"
    Combo1.ListIndex = 0 ' Select first item
End Sub

This VB.NET implementation uses Windows Forms with similar controls but includes better error handling and modern features.

Public Class CalculatorForm
    Private Sub ComboBox1_SelectedIndexChanged(sender As Object, e As EventArgs) Handles ComboBox1.SelectedIndexChanged
        Call CalculateResult()
    End Sub

    Private Sub CalculateButton_Click(sender As Object, e As EventArgs) Handles CalculateButton.Click
        Call CalculateResult()
    End Sub

    Private Sub CalculateResult()
        Dim num1, num2, result As Double
        
        ' Validate and parse first number
        If Not Double.TryParse(TextBox1.Text, num1) Then
            MessageBox.Show("Please enter a valid number in the first field", "Input Error", 
                            MessageBoxButtons.OK, MessageBoxIcon.Exclamation)
            Return
        End If
        
        ' Validate and parse second number
        If Not Double.TryParse(TextBox2.Text, num2) Then
            MessageBox.Show("Please enter a valid number in the second field", "Input Error", 
                            MessageBoxButtons.OK, MessageBoxIcon.Exclamation)
            Return
        End If
        
        ' Perform calculation based on selected operator
        Select Case ComboBox1.SelectedIndex
            Case 0 ' Addition
                result = num1 + num2
            Case 1 ' Subtraction
                result = num1 - num2
            Case 2 ' Multiplication
                result = num1 * num2
            Case 3 ' Division
                If num2 = 0 Then
                    MessageBox.Show("Cannot divide by zero", "Math Error", 
                                    MessageBoxButtons.OK, MessageBoxIcon.Exclamation)
                    Return
                End If
                result = num1 / num2
        End Select
        
        ' Display formatted result
        ResultLabel.Text = result.ToString("N2")
    End Sub

    Private Sub ExitButton_Click(sender As Object, e As EventArgs) Handles ExitButton.Click
        Me.Close()
    End Sub

    Private Sub CalculatorForm_Load(sender As Object, e As EventArgs) Handles MyBase.Load
        ' Initialize combo box with operators
        ComboBox1.Items.AddRange(New Object() {"+", "-", "×", "÷"})
        ComboBox1.SelectedIndex = 0
    End Sub
End Class

Implementation Details

Both VB6 and VB.NET implementations follow similar logic but with important differences in syntax and error handling:

VB6 Implementation

Form Controls: Uses TextBox, ComboBox, Label, and CommandButton controls
Event Handling: Uses event procedures like Combo1_Change and Command1_Click
Input Validation: Uses IsNumeric() to check for valid numbers
Error Handling: Displays message boxes for errors
Division by Zero: Explicit check to prevent calculation errors

VB.NET Implementation

Modern Controls: Similar controls but with improved properties and events
Better Validation: Uses Double.TryParse() for more robust number parsing
Structured Error Handling: Uses MessageBox for user-friendly error messages
Resource Management: Automatic resource cleanup with garbage collection
Event Handling: Uses Handles keyword for cleaner event attachment

Tip: When migrating from VB6 to VB.NET, pay special attention to:

Data type changes (e.g., Integer is now 32-bit instead of 16-bit)
Control property name changes
Improved error handling with Try/Catch blocks
Object-oriented features in VB.NET