VB Tip: How to auto-find in a List Box
When a List Box control has the focus, it will automatically scroll to the first item that begins with the letter you type. It will not, however, automatically select items based on more than the first letter. For example, if you type ap, you may want the control to select the first item that begins with ap. This tip explains how you can implement this behavior using the API function SendMessage. Its declaration, which must be included in the program, is as follows:
Public Declare Function SendMessage Lib "user32" _
Alias "SendMessageA" (ByVal hwnd As Long, _
ByVal wMsg As Long, ByVal wParam As Long, _
ByVal lParam As String) As Long
You'll also need the following constant, which tells the List
Box control to select the first item that begins with the specified
prefix:
Public Const LB_SELECTSTRING = &H18C
In addition to the List Box, this technique requires a Text Box
control. The user enters text in the Text Box, and the List Box
automatically selects the first matching item. The message is sent in
the Text Box's Change event procedure:
Private Sub Text1_Change()
If Text1.Text <> "" Then
SendMessage List1.hwnd, LB_SELECTSTRING, -1, Text1.Text
End If
End Sub
Letting the user select List Box items based on more than just the
first letter can be particularly useful when the list contains many
items.
Peter Aitken has been programming with Visual Basic since Version
1.0. He has written numerous books and magazine articles on Visual
Basic and other computer and programming topics.