List Box Cumulative Search

List Box Cumulative Search

By default, VB list boxes use any keyboard input to find the firstitem beginning with the pressed letter. Where the number of itemsin a list box is large (>100), this is not helpful. Substitutinga binary or hybrid search for the sequential search below speedsup the algorithm substantially for very large lists (>1000items). The code below searches the items in a sorted list boxbased on all the characters typed by the user:

 Global ListBoxSearch$Sub ListBox_KeyPress (KeyAscii As _        Integer)        'Return KeyAscii in case you         'want VB to handle certain charsKeyAscii = SearchListBox_        (Me.ActiveControl, KeyAscii)End SubFunction SearchListBox _        (CurrentActiveControl As Control, _        KeyAscii As Integer)        Dim ListBoxIndex As Integer        Dim Result As Integer                   'Result of string compare        ListBoxSearch$ = ListBoxSearch$ & _                Chr$(KeyAscii)        ListBoxIndex = CurrentActive_                Control.ListIndex While ListBoxIndex < CurrentActive_        Control.ListCount        Result = StrComp(UCase$(List_                BoxSearch$), UCase$(Left$_                (CurrentActiveControl.List_                (ListBoxIndex), Len(ListBox_                Search$))))         If Result <= 0 Then                 CurrentActiveControl.List_                        Index_= ListBoxIndex                 SearchListBox = 0                 Exit Function         End If         ListBoxIndex = ListBoxIndex + 1 Wend ListBoxIndex = CurrentActive_        Control.ListCount - 1 CurrentActiveControl.ListIndex_         = ListBoxIndex SearchListBox = 0End Function

Note: Clearly, the code above is not complete and needs to beaugmented to suit the individual developer. For example, whento clear ListBoxSearch$ is a subject of much consideration (activecontrol changes, user presses arrow keys, and so forth) I implementedthe above scheme on a list of >1500 items with a separate ClearLBSearchsubroutine and a binary/sequential hybrid searching algorithm.

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