FoxPro multiselect listbox
The standard listbox control in Visual FoxPro allows the user to easily
select an item from the list that is displayed. If you set the
property of the listbox then you can let the user make multiple selections
from the list. These selections follow the usual conventions of the
Windows user interface:
- Click on a row to select or deselect a single item.
- Hold down CTRL and click to add an item to a selection.
-
Hold down CTRL and click on a selected item to remove it from a
selection.
-
Hold down SHIFT and click to extend a selection
Coding for multiple selections
The first step is to set the MultiSelect property of the listbox to .T..
This enables the behaviour described above. The listbox has a Selected
property which is an array with one element for every row in the
listbox. When a row is selected a value of .T. is stored in the
equivalent member of this property array. Scan the array to determine
which rows have been selected.
In the example below, the InteractiveChange event of the listbox calls the
following code to create the list of selected items:
With Thisform
.edtSelected.Value = ""
For
ln = 1
To
.lstMulti.ListCount
If
.lstMulti.Selected(ln)
.edtSelected.Value = .edtSelected.Value + ;
.lstMulti.List(ln) + Chr(13)
Endif
Next
ln
EndWith
Similar loops behind the
and
buttons set all elements of the array to .T. and .F.
respectively.
Other listbox properties
By default the selected items will appear in the standard
colours from the user's Windows colour scheme. You can
override these with the
and
properties but remember that the user may have taken great care
in chosing their own colour scheme to suit their own requirements.
To take an extreme example, a user with some form of red/green
colour blindness would not be pleased if you ignored their own
preferences and displayed selected items in red and green.
Alternatives
The listbox with its
property is an easy way of letting your user make multiple
selections but not all users know of the Windows conventions for selecting several
items. Consider using a
grid with checkboxes if you
need a more sophisticated interface. This technique also allows you to add a very useful
pair of "Tick All" and "Clear All" buttons.
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