Computer Programming Concepts and Visual Basic David I. Schneider

sales = 0
For depNum = 0 To 4
sales = sales + Val(txtSales(depNum).Text)
Next depNum
picTotal.Cls
picTotal.Print “Total sales were ”; FormatCurrency(sales)
End Sub
[Run, type the following data into the text boxes, and click the command button.]
■ CONTROL ARRAY EVENT PROCEDURES
In Section 3 we discussed several events related to text boxes. One example was the GotFocus
event procedure. If txtBox is an ordinary text box, then the GotFocus event procedure begins
with the statement
Private Sub txtBox_GotFocus()
If, on the other hand, we make txtBox a control array, the GotFocus event procedure begins with
the statement
Private Sub txtBox_GotFocus(Index As Integer)
Two points should be noted. First, even though we may have a dozen or more elements in the
txtBox( ) control array, we will have just one txtBox_GotFocus event procedure to deal with.
Second, Visual Basic passes to this one event procedure the value of the Index property for the
element of the control array that has just received the focus. We may wish to respond in the
same manner whenever any element of txtBox( ) has the focus, in which case we simply ignore
the value of Index. If, on the other hand, we wish to respond in different ways, depending on
which element has the focus, then we write the GotFocus event procedure in the form
Private Sub txtBox_GotFocus(Index As Integer)
Select Case Index
Case 0
action when txtBox( ) gets the focus
Case 1
action when txtBox(1) gets the focus . .
End Select
End Sub
In general, all event procedures for a control array have the additional parameter Index As
Integer. This additional parameter can be used, if desired, to base the action taken by the event
procedure on which element of the control array underwent the event.
EXAMPLE 2
The following program creates an electronic dialing pad. The form contains a control array of 10 command
buttons. Each time a command button is clicked, the Index parameter conveys the digit to be added
onto the phone number. This program illustrates using the Index parameter without employing a Select
Case statement.
Control Arrays 181