Q308644: BUG: Memory Leak When You Bind Recordset to VB Intrinsic Control

Article: Q308644
Product(s): Microsoft Visual Basic for Windows
Version(s): 6.0
Operating System(s): 
Keyword(s): 
Last Modified: 16-MAY-2002

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The information in this article applies to:

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

If your Visual Basic application includes Visual Basic intrinsic controls (such
as TextBox controls) on the form, when the code repeatedly binds a Recordset
object to the control with the DataSource property of the control, you may
notice that memory usage grows while the application runs.

CAUSE
=====

This problem occurs because the Recordset object is not released even if you set
DataSource to Nothing.

RESOLUTION
==========

A supported fix that corrects this problem is now available from Microsoft, but
it has not been fully regression tested and should be applied only to computers
that are experiencing this specific problem.

NOTE: You must have a Visual Studio license agreement to obtain this fix.

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 on support costs, please go to the following address on the World
Wide Web:

  http://support.microsoft.com/default.aspx?scid=fh;EN-US;CNTACTMS

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

  Date        Time  Version      Size     File name
  ----------------------------------------------------
  25-Sep-2001 8:03  6.0.93.63    1.33 MB  MSVBVM60.dll  
  25-Sep-2001 8:03  6.0.93.63    1.79 MB  VB6.exe 



STATUS
======

Microsoft has confirmed this to be a bug in the Microsoft products listed at the
beginning of this article.

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

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

1. Create a new Standard EXE application in Visual Basic. Form1 is created by
  default.

2. On the Project menu, click References. Select the "Microsoft ActiveX Data
  Objects 2.x Library" check box, and then click OK.

3. Place a TextBox control and a CommandButton control on Form1. Keep the
  default names for these two controls.

4. Add the following code to the code window of Form1:

  Option Explicit

  Private mRecordset  As ADODB.Recordset

  Private Sub ClearDataSource()
      Text1.DataField = vbNullString
      Set Text1.DataSource = Nothing
      Set mRecordset = Nothing
  End Sub

  Private Sub Command1_Click()

      Dim lOffset As Integer
      
      For lOffset = 1 To 100 Step 1
          ClearDataSource
          CreateADO
          Text1.DataField = "firstname"
          Set Text1.DataSource = mRecordset
      Next lOffset
  End Sub

  Private Sub CreateADO()
      Set mRecordset = New Recordset
      mRecordset.CursorLocation = adUseClient
      mRecordset.LockType = adLockBatchOptimistic
      Set mRecordset.ActiveConnection = Nothing

      mRecordset.Fields.Append "firstname", adVarChar, 10
      mRecordset.Open 
      mRecordset.AddNew
      mRecordset(0) = "Joe"
      mRecordset.MoveFirst
  End Sub

5. Build and run the application.

6. Click the command button repeatedly. Use Performance Monitor or Task Manager
  to monitor the memory usage.

Additional query words:

======================================================================
Keywords          :  
Technology        : kbVBSearch kbAudDeveloper kbZNotKeyword6 kbZNotKeyword2 kbVB600Search kbVB600
Version           : :6.0
Hardware          : ALPHA x86
Issue type        : kbbug
Solution Type     : kbpending

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