Q190042: PRB: License Collection vs. Standard Collection in For Each

Article: Q190042
Product(s): Microsoft Visual Basic for Windows
Version(s): WINDOWS:6.0;
Operating System(s): 
Keyword(s): kbnokeyword kbVBp600 kbGrpDSVB
Last Modified: 11-JAN-2001

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The information in this article applies to:

- Microsoft Visual Basic Learning Edition for Windows, version 6.0 
- Microsoft Visual Basic Professional Edition for Windows, version 6.0 
- Microsoft Visual Basic Enterprise Edition for Windows, version 6.0 
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SYMPTOMS
========

The Licenses Collection handles the removal of elements differently from a
standard VBA Collection object when you use it in a For Each loop. In a standard
VBA Collection, if an item is removed during a For Each loop, the collection
recognizes that the item is no longer an element and does not attempt to iterate
over that element. In the Licenses collection, if an item is removed or the
collection is cleared, the For...Each loop still iterates over that element of
the collection. It does not recognize any changes made to the collection during
the loop.

RESOLUTION
==========

Do not attempt to access the members of the Licenses Collection in the same loop
in which you are removing elements of the collection. Remove the unwanted
licenses using the Clear or Remove methods before iterating over the collection
in a For...Each loop. If you need to use a loop when removing elements, use two
separate loops: one to remove the elements and one to access the remaining
elements. See step 4 in the MORE INFORMATION section of this article for an
example.

STATUS
======

This behavior is by design.

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

Steps to Reproduce Behavior
---------------------------

1. Start a new Standard EXE project is Visual Basic. Form1 is created by
  default.

2. Add the following code to the module of Form1.

        Private Sub Form_Load()
           Dim x As Variant
           Licenses.Add "RichText.RichTextCtrl"
           Licenses.Add "MSDBGrid.DBGrid"
           For Each x In Licenses
              Licenses.Clear
              MsgBox x
           Next
        End Sub

3. Run the project. The message boxes display the elements of the collection
  even though they have been "cleared."

4. Stop the project and replace the code in step 2 with the following:

        Private Sub Form_Load()
          Dim x As Variant
          Licenses.Add "RichText.RichTextCtrl"
          Licenses.Add "MSDBGrid.DBGrid"
          Licenses.Clear
          For Each x In Licenses
             MsgBox x
          Next
        End Sub

5. Run the project.

RESULT: The message boxes no longer appear.

Additional query words:

======================================================================
Keywords          : kbnokeyword kbVBp600 kbGrpDSVB 
Technology        : kbVBSearch kbAudDeveloper kbZNotKeyword6 kbZNotKeyword2 kbVB600Search kbVBA600 kbVB600
Version           : WINDOWS:6.0;
Issue type        : kbprb

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