Maximum Number Calculator | VB6 & VB.NET Example

This program allows the user to enter three numbers and calculates the maximum number among them. The solution demonstrates how to implement this functionality in both Visual Basic 6 and Visual Basic .NET.

Key programming concepts demonstrated:

Function creation with parameters
Conditional logic using If-Then-Else statements
Comparison operators
Data type conversion
Event handling for button clicks

Interactive Calculator

Enter three numbers to find the maximum value:

Number 1:

Number 2:

Number 3:

Result will appear here

15

27

8

Code Implementation

Below are implementations in both Visual Basic 6 and Visual Basic .NET:

 Visual Basic 6 Implementation
                    ' Function to calculate maximum of three numbers
Function calMax(x As Variant, y As Variant, z As Variant) As String
    If x > y And x > z Then
        calMax = Str(x)
    ElseIf y > x And y > z Then
        calMax = Str(y)
    ElseIf z > x And z > y Then
        calMax = Str(z)
    Else
        ' If all numbers are equal
        calMax = Str(x)
    End If
End Function

' Button click event handler
Private Sub Command1_Click()
    Dim a, b, c As Double
    
    ' Get values from text boxes
    a = Val(Txt_Num1.Text)
    b = Val(Txt_Num2.Text)
    c = Val(Txt_Num3.Text)
    
    ' Display result in label
    Lbl_Display.Caption = calMax(a, b, c)
End Sub
                

 Visual Basic .NET Implementation
                    ' Function to calculate maximum of three numbers
Private Function CalculateMax(ByVal x As Double, 
                          ByVal y As Double, 
                          ByVal z As Double) As String
    
    If x > y AndAlso x > z Then
        Return x.ToString()
    ElseIf y > x AndAlso y > z Then
        Return y.ToString()
    ElseIf z > x AndAlso z > y Then
        Return z.ToString()
    Else
        ' If all numbers are equal
        Return x.ToString()
    End If
End Function

' Button click event handler
Private Sub btnCalculate_Click(sender As Object, 
                             e As EventArgs) Handles btnCalculate.Click
    Dim num1, num2, num3 As Double
    
    ' Parse input values with validation
    If Not Double.TryParse(txtNum1.Text, num1) Then
        MessageBox.Show("Please enter a valid number in field 1")
        Exit Sub
    End If
    
    If Not Double.TryParse(txtNum2.Text, num2) Then
        MessageBox.Show("Please enter a valid number in field 2")
        Exit Sub
    End If
    
    If Not Double.TryParse(txtNum3.Text, num3) Then
        MessageBox.Show("Please enter a valid number in field 3")
        Exit Sub
    End If
    
    ' Calculate and display result
    lblResult.Text = "Maximum number: " & CalculateMax(num1, num2, num3)
End Sub
                

Note: The VB.NET version includes input validation and uses type-safe methods, demonstrating modern best practices.

Key Differences Between VB6 and VB.NET

Syntax

VB.NET uses AndAlso/OrElse for short-circuit evaluation instead of And/Or

Type Safety

VB.NET requires explicit data types and uses TryParse for safe conversion

Event Handling

VB.NET uses Handles clause instead of object-specific event procedures

Error Handling

VB.NET encourages structured exception handling with Try/Catch blocks