Control Arrays

[taxes]

Hi,

A common misconception is that Control Arrays have disappeared from VB.NET. They haven't. What has disappeared is the Index Property of a control and the ability to create the array automatically in design view.

MSDN Help will give several work-arounds, including use of the Tag property but the simplest way is to use an Array of Controls. The following creates ten textboxes in code and stores a reference to each one in an array.

Dim arrTextBox(0) As TextBox  ' (Prepare array to receive textBoxes.
                                                 '  Give this the necesary scope)
 
    Private Sub Button3_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button3.Click
 
        Dim txtTemp As TextBox       '   ( Reserve variable for new textbox
                                                '   Local scope only  OK)
        Dim iCount As Integer              (Local scope only)
 
        For iCount = 0 To 9
            ReDim Preserve arrTextBox(iCount)  '(Expand array to receive
                                                                 ' next textbox
            txtTemp = New TextBox   ' ( Create instance of new textbox)
            txtTemp.Name = "txtBox" & iCount.ToString  '(Name textboxes with
                                                                        'sequential numbering)
            txtTemp.Width = 40
            txtTemp.Location = New Point(15, iCount * 20)
            Me.Controls.Add(txtTemp)           '(Add new textbox to form
            arrTextBox(iCount) = txtTemp      '(Place reference to new textbox
                                                          'in appropriate element of array)
 
'(The next line adds the handle of the new textbox to the appropriate event)
 
            AddHandler txtTemp.TextChanged, AddressOf TextChangedEvent  
        Next
End Sub
 
 
     Private Sub TextChangedEvent(ByVal sender As System.Object, ByVal e As System.EventArgs)
        MessageBox.Show(CType(sender, TextBox).Name & "  Text was changed")
    End Sub

You can now refer to each TextBox by the array subscript ( index no.)

This is better than the VB6 Control Array because you can mix any type of object by replacing

Dim txtTemp As TextBox
Dim arrTextBox() As TextBox
txtTemp = New TextBox

with

Dim txtTemp As Object
Dim arrTextBox() As Object
txtTemp = New Object

You could then widen the possibilities by using a 2 dimension array, allocating the elements of the first dimension to hold different types or groups of objects, although those elements would only hold numeric values of course.


EDIT; Handler for Text_Changed event added, see Wossname's comment.