Q136640: How to Fill a Combo Box with a Unique List of Items

Article: Q136640
Product(s): Microsoft FoxPro
Version(s): WINDOWS:3.0
Operating System(s): 
Keyword(s): 
Last Modified: 04-AUG-2000

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The information in this article applies to:

- Microsoft Visual FoxPro for Windows, version 3.0 
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SUMMARY
=======

To have a combo box display unique values from a field of a database that
contains multiple occurrences of each of those values, use the DisplayValue
property in combination with the ListIndex property of the combo box.

MORE INFORMATION
================

Placing a string in the combo box DisplayValue property automatically sets the
combo box ListIndex property to zero (0) if no match is found or to the index
position of a matching string within the created list. Therefore, you can loop
through until the ListIndex property is 0, and then add the new list item by
using the AddItem method. By using a SCAN...ENDSCAN looping structure, you can
create a completely unique list as the following example code illustrates.

Sample Code
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Place the following code in the combo box Init event to create a unique list of
the <field name> contents before displaying the combo box:

     * Init Code
     SCAN
        THIS.DISPLAYVALUE = <field name>
        IF THIS.LISTINDEX = 0      && not already in the list
           THIS.ADDITEM(<field name>)
        ENDIF
     ENDSCAN
     THISFORM.REFRESH

If a new item is typed into the combo box, it must be verified as unique before
being added to the current list. To force the ListIndex property to change
automatically, add the following code to the Valid event procedure of the combo
box:

     * Valid Code
     THIS.VALUE = THIS.DISPLAYVALUE
     IF THIS.LISTINDEX = 0      && Not already in the list
        THIS.ADDITEM(THIS.VALUE)
        THIS.DISPLAYVALUE = THIS.VALUE
     ENDIF

The code assigns the DisplayValue property to the Value property for the combo
box. Then it checks the value of ListIndex. If ListIndex is 0, the item is added
as before. When this comparison is made, the DisplayValue property loses its
contents, so the Value property is reassigned to the DisplayValue property in
the IF...ENDIF structure.

(c) Microsoft Corporation 2000, All Rights Reserved. Contributions by Kevin
Zollman, Microsoft Corporation.


Additional query words: VFoxWin akz

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Keywords          :  
Technology        : kbVFPsearch kbAudDeveloper kbVFP300
Version           : WINDOWS:3.0

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