Lesson 16: Mastering Sub Procedures in VB2022

Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
    ' Call the sub procedure with two numbers
    Sum(5, 6)
End Sub

' Define the sum sub procedure
Sub Sum(a As Single, b As Single)
    ' Display the result in a message box
    MsgBox("The sum is: " & (a + b))
End Sub

Public Class Form1
    Dim password As Integer
    Dim crackpass As Integer
    
    Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
        ' Start the password generation process
        Timer1.Enabled = True
    End Sub
    
    Private Sub Timer1_Tick(sender As Object, e As EventArgs) Handles Timer1.Tick
        ' Generate a new password attempt
        GeneratePassword()
        
        ' Check if password is found
        If crackpass = password Then
            Timer1.Enabled = False
            Label1.Text = crackpass
            MsgBox("Password Cracked! Login Successful!")
        Else
            Label1.Text = crackpass
            Label2.Text = "Please wait..."
        End If
    End Sub
    
    ' Sub procedure to generate password attempts
    Sub GeneratePassword()
        ' Generate a random number between 100 and 199
        crackpass = Int(Rnd() * 100) + 100
    End Sub
    
    Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
        ' Set the actual password
        password = 123
    End Sub 
End Class

Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
    Dim num As Integer = 5
    ModifyValue(num)
    MessageBox.Show("Original value: " & num) ' Output: 5
End Sub

Sub ModifyValue(ByVal value As Integer)
    value = 10
End Sub

Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
    Dim num As Integer = 5
    ModifyReference(num)
    MessageBox.Show("Modified value: " & num) ' Output: 10
End Sub

Sub ModifyReference(ByRef value As Integer)
    value = 10
End Sub

Private Sub btnSubmit_Click(sender As Object, e As EventArgs) Handles btnSubmit.Click
    If Not ValidateEmail(txtEmail.Text) Then
        MsgBox("Please enter a valid email address")
        Return
    End If
    
    If Not ValidateAge(txtAge.Text) Then
        MsgBox("Please enter a valid age (18-99)")
        Return
    End If
    
    ProcessRegistration()
End Sub

' Email validation procedure
Function ValidateEmail(email As String) As Boolean
    Return email.Contains("@") And email.Contains(".")
End Function

' Age validation procedure
Function ValidateAge(ageText As String) As Boolean
    Dim age As Integer
    Return Integer.TryParse(ageText, age) AndAlso age >= 18 AndAlso age <= 99
End Function

' Registration processing
Sub ProcessRegistration()
    ' Code to process registration
    MsgBox("Registration successful!")
End Sub

Private Sub btnConvert_Click(sender As Object, e As EventArgs) Handles btnConvert.Click
    Dim celsius As Double
    Dim fahrenheit As Double
    
    If Not Double.TryParse(txtCelsius.Text, celsius) Then
        MsgBox("Please enter a valid number")
        Return
    End If
    
    ' Convert to Fahrenheit
    CelsiusToFahrenheit(celsius, fahrenheit)
    lblFahrenheit.Text = fahrenheit.ToString("F1")
End Sub

' Conversion procedure
Sub CelsiusToFahrenheit(ByVal c As Double, ByRef f As Double)
    f = (c * 9 / 5) + 32
End Sub

Private Sub btnDraw_Click(sender As Object, e As EventArgs) Handles btnDraw.Click
    Dim g As Graphics = PictureBox1.CreateGraphics()
    
    ' Clear the picture box
    g.Clear(Color.White)
    
    ' Draw different shapes
    DrawCircle(g, 50, 50, 40, Color.Red)
    DrawRectangle(g, 150, 50, 80, 60, Color.Blue)
    DrawTriangle(g, 300, 50, 60, Color.Green)
End Sub

' Circle drawing procedure
Sub DrawCircle(g As Graphics, x As Integer, y As Integer, diameter As Integer, color As Color)
    Dim pen As New Pen(color, 3)
    g.DrawEllipse(pen, x, y, diameter, diameter)
End Sub

' Rectangle drawing procedure
Sub DrawRectangle(g As Graphics, x As Integer, y As Integer, width As Integer, height As Integer, color As Color)
    Dim pen As New Pen(color, 3)
    g.DrawRectangle(pen, x, y, width, height)
End Sub

' Triangle drawing procedure
Sub DrawTriangle(g As Graphics, x As Integer, y As Integer, size As Integer, color As Color)
    Dim pen As New Pen(color, 3)
    Dim points() As Point = {
        New Point(x, y + size),
        New Point(x + size / 2, y),
        New Point(x + size, y + size)
    }
    g.DrawPolygon(pen, points)
End Sub