How to Limit the Number of Characters Typed in a Combo Box

Last reviewed: October 25, 1995
Article ID: Q138499

The information in this article applies to:

Microsoft Visual FoxPro for Windows, version 3.0

SUMMARY

You can limit the number of characters that a user can type into a text box by using the InputMask property. However, this property does not exist for a combo box. This article shows shows by example how to limit the number of characters typed in a combo box by placing code in the KeyPress event.

MORE INFORMATION

Step-by-Step Example

Create a new form.

On the Form menu, click New Property, and name the new property numb.

Place a combo box on the form, and set its ControlSource, RowSourceType, and RowSource properties.

Place at least one other control on the form.

Place the following code in the KeyPress event for the combo box to limit the number of characters entered into the combo box to 3:

   IF nKeyCode=13 OR nKeyCode=9   && test for ENTER or TAB
     THISFORM.numb=0              && and reset numb
   ELSE
     IF !(nkeyCode=127 OR ;       &&  BACKSPACE
       nkeyCode=7 OR ;            &&  DELETE
       nkeyCode=6 OR ;            &&  END key
       nkeyCode=19 OR ;           &&  LEFT ARROW
       nkeyCode=4 OR ;            &&  RIGHT ARROW
       nkeyCode=1)                &&  HOME key
       THISFORM.numb=THISFORM.numb+1  && if not one of the above increment

         IF THISFORM.numb=4       && When 4 characters have been entered
           THISFORM.numb=0        && reset numb to zero and flash a message
           ?? CHR(7)              && ring the bell
           =MESSAGEBOX("Enter only 3 characters")
           NODEFAULT              &&  do not enter the character typed.
         ENDIF
     ENDIF
   ENDIF

Additional reference words: 3.00 VFoxWin mask format
KBCategory: kbprg kbcode kbhowto
KBSubcategory: FxotherGeneral

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Last reviewed: October 25, 1995
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