Microsoft KB Archive/247797

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Extra Unexpected LBN_SELCHANGE Notification for Drop-Down List Boxes in Windows NT 4.0

Article ID: 247797

Article Last Modified on 11/1/2006


  • Microsoft Windows NT Server 4.0 Standard Edition
  • Microsoft Windows NT Workstation 4.0 Developer Edition

This article was previously published under Q247797


Windows NT 4.0 generates an LBN_SELCHANGE notification for drop-down list boxes in the following circumstances:

  1. The user clicks the arrow on the right side of the drop-down list box to drop the list down.
  2. The user moves the mouse pointer down the list causing various items in the list to be selected, but does not click any item.
  3. The user moves the mouse pointer outside the list box, and then clicks the mouse to close the drop-down list.

At this point, a sequence of windows messages are sent to the program. Under Windows NT 4.0, this includes an extraneous LBN_SELCHANGE notification for the list box. It is incorrect to send an LBN_SELCHANGE notification at this point because clicking outside of a dropped-down list box to close it as described above does not change the current selection in the list box.

Microsoft Visual Basic programs may see this as an extra Click event if a Click method is defined for the list box.

Some programs that run without problems under Windows NT 3.51 may malfunction when they receive this unexpected notification under Windows NT 4.0.


A supported fix is now available from Microsoft, but it is only intended to correct the problem that is described in this article. Apply it only to computers that are experiencing this specific problem.

To resolve this problem, contact Microsoft Product Support Services to obtain the fix. For a complete list of Microsoft Product Support Services phone numbers and information about support costs, visit the following Microsoft Web site:

NOTE: In special cases, charges that are ordinarily incurred for support calls may be canceled if a Microsoft Support Professional determines that a specific update will resolve your problem. The usual support costs will apply to additional support questions and issues that do not qualify for the specific update in question.

The English version of this fix should have the following file attributes or later:

   Date      Time                 Size    File name     Platform
   10/12/99  00:58                326,416 User32.dll    Intel
   10/12/99  00:57                577,296 User32.dll    Alpha


Recode the program to handle the extra notification gracefully.


Microsoft has confirmed that this is a problem in the Microsoft products that are listed at the beginning of this article.

Keywords: kbhotfixserver kbqfe kbbug kbfix KB247797