Lesson 15: Looping in VB2019

Private Sub BtnGenerate_Click(sender As Object, e As EventArgs) Handles BtnGenerate.Click
    Dim counter As Integer
    
    For counter = 1 To 10
        ListBox1.Items.Add(counter)
    Next
End Sub

Private Sub BtnEvenNumbers_Click(sender As Object, e As EventArgs) Handles BtnEvenNumbers.Click
    Dim counter As Integer
    
    For counter = 0 To 20 Step 2
        ListBox1.Items.Add(counter)
    Next
End Sub

Private Sub BtnValidate_Click(sender As Object, e As EventArgs) Handles BtnValidate.Click
    Dim userInput As Integer
    
    Do
        userInput = Val(InputBox("Enter a positive number:"))
    Loop Until userInput > 0
    
    LblResult.Text = "You entered: " & userInput
End Sub

Private Sub BtnCountdown_Click(sender As Object, e As EventArgs) Handles BtnCountdown.Click
    Dim count As Integer = 10
    
    While count >= 1
        ListBox1.Items.Add(count)
        count -= 1
    End While
    
    ListBox1.Items.Add("Liftoff!")
End Sub

Private Sub BtnCheckPrime_Click(sender As Object, e As EventArgs) Handles BtnCheckPrime.Click
    Dim num As Integer = Val(TxtNumber.Text)
    Dim isPrime As Boolean = True
    
    If num <= 1 Then
        isPrime = False
    Else
        For i = 2 To Math.Sqrt(num)
            If num Mod i = 0 Then
                isPrime = False
                Exit For
            End If
        Next
    End If
    
    If isPrime Then
        LblResult.Text = num & " is a prime number"
    Else
        LblResult.Text = num & " is not a prime number"
    End If
End Sub