Practice 4 Visual Basic Loops

1. Put a textbox, a listbox, and a button on the form. The user must enter a number and press the button. When the button is pressed, it will add that many items to the listbox on the form.

   Private Sub theButton_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles theButton.Click  
     Dim times As Double  
     times = CDbl(TextBox1.Text)  
     Dim i, sum As Integer  
     sum = 0  
     For i = 1 To times  
       sum = sum + 1  
       'show items in listbox  
       ListBox1.Items.Add(sum & " items")  
     Next  
   End Sub  
 End Class  

2. If you were to put away a certain amount of money every month, how many years would it take you to save up $10,000. Use a textbox to gather the amount that is to be put away every month. Use a label to display the number of years it would take.

 Public Class Form1  
   Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click  
     Dim pay, months, total, goal As Integer  
     Dim years As Decimal  
     pay = CInt(txtPay.Text)  
     goal = 10000  
     For total = 1 To goal  
       total += pay  
       months = months + 1  
       years = months / 12  
       Label3.Text = ("It will take " & years.ToString("f1") & " years to make the $10,000 goal.")  
     Next  
   End Sub  
 End Class  

3. Write a program that will create a times table.

1 2 3 4 5 6 7 8 9 10
2 4 6 8 10 12 14 16 18 20
…..
You could use labels or buttons to hold the numbers. Generate these dynamically and add them to the Me.Controls collection.
You will have to use two loops, one inside of the other to get this to work.

 Public Class Form1  
   Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click  
     Dim x, y As Integer  
     'Button = 20 pixels  
     x = 1  
     Button1.Visible = False  
     For x = 1 To 10  
       For y = 1 To 10  
         Dim newbutton As New Button  
         newbutton.Location = New Point(50 * x, 50 * y)  
         newbutton.Width = 40  
         newbutton.Text = x * y  
         Me.Controls.Add(newbutton)  
       Next  
     Next  
   End Sub  
 End Class  

A loop within a loop operates in the inside loop until that loop is finished, then goes into the outer loop to get to the next level to run the inner loop again till it is finished.