Fast Lookup in FoxPro

If you want to let users make a fast choice from values in a table then you normally use a combo or list box. This technique works well until you need to work with a large table. The technique described here lets the user choose from a million and a half postcodes.

When the user enters each character of the postcode the textbox finds and displays the first address which matches that partial code. The sample shows the situation after the user has typed 'B4'. The first entry with this code is 'B4 6AA' and the matching address is displayed.
If the user goes on to type 'B41' - a non-existent postcode - then the address changes to show 'Not found' and the postcode itself turns red. As the user backspaces to delete the '1', the address reverts to the last good entry matching 'B4'.

The autocomplete of the postcode field and the display of the address happen as quickly as the user can enter and delete characters into the textbox. A combobox populated with the million and a half postcodes took minutes to load and ran very slowly.

How to do it

The code to achieve this effect is surprisingly simple. The form itself opens the PostCode table and sets it in PostCode order. All the rest is done by the InteractiveChange method of the textbox:

If you are using VFP 9 then you can use the new AutoComplete property of the textbox to get much the same effect without any coding at all.

Workshop course

This particular requirement came up during a workshop course. We went on to convert the textbox into a self-contained control and save it as a class. This class has properties such as cTableName, cOrder, cSearchField and cDisplayField and can be dropped onto any form in order to provide a fast lookup facility.