Knowledge Base

PRB: License Collection vs. Standard Collection in For Each

Article ID: 190042

Article Last Modified on 5/12/2003

Microsoft Visual Basic 6.0 Learning Edition
Microsoft Visual Basic 6.0 Professional Edition
Microsoft Visual Basic 6.0 Enterprise Edition

This article was previously published under Q190042

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

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

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

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

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

Run the project.

RESULT: The message boxes no longer appear.

Keywords: kbprb KB190042