DOCUMENT:Q253211  23-AUG-2001  [vbwin]
TITLE   :PRB: Large Recordsets Cause Problems When Scrolling Grids
PRODUCT :Microsoft Visual Basic for Windows
PROD/VER::2.0,2.1 SP2,2.5,2.6,6.0
OPER/SYS:
KEYWORDS:kbDatabase kbDataBinding kbVBp600 kbVBp600bug kbGrpDSVBDB kbGrpDSMDAC kbDSupport kbMDAC

======================================================================
-------------------------------------------------------------------------------
The information in this article applies to:

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

SYMPTOMS
========

Using very large recordsets with the Microsoft DataGrid Control 6.0 or the
Microsoft Hierarchical FlexGrid Control 6.0 can cause problems when scrolling
the grid. When the user drags the thumbtrack to the bottom of the vertical
scrollbar, the thumbtrack might jump back to the top. This happens whenever the
top row of the grid would have been greater than 65,535.

RESOLUTION
==========

Limit the recordset to fewer than 65,536 records. While the grid can display
more rows, you cannot use the thumbtrack to scroll past this number.

This bug does not show up in the OLEDB version of the APEX True DBGrid.

STATUS
======

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

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

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

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

2. On the Project menu, select References, and add Microsoft ActiveX Data
   Objects 2.x Library.

3. On the Project menu, select Components, and add the following:

   Microsoft DataGrid Control 6.0 (OLEDB)
   Microsoft Hierarchical FlexGrid Control 6.0 SP3 (OLEDB)

4. Place two Command buttons, a DataGrid, and a MSHFlexGrid on Form1.

5. Place the following code into Form1:

   Option Explicit

   Dim rs As ADODB.Recordset

   Private Sub Command1_Click()
      Set rs = New ADODB.Recordset
      With rs
         .Fields.Append "Record Number", adBigInt
         
         .Open
         
         Dim x As Long
         For x = 1 To 65535
            .AddNew
            ![Record Number] = x
            .Update
         Next x
      End With
      
      Set DataGrid1.DataSource = rs
      Set MSHFlexGrid1.DataSource = rs
      Command2.Enabled = True
   End Sub

   Private Sub Command2_Click()
      Dim x As Long
      With rs
         For x = 1 To 5
            .AddNew
            ![Record Number] = .RecordCount
            .Update
         Next x
      End With
      
      Set MSHFlexGrid1.DataSource = rs
   End Sub

   Private Sub Form_Load()
      Command1.Caption = "Add 64K"
      Command2.Caption = "Add 5"
      Command2.Enabled = False
   End Sub

6. Run the code and click Add 64K. Drag the thumbtrack to the bottom of the
   vertical scrollbar on each grid, and note that the grids scroll properly.

7. Click the Add 5 Command button until you have enough records to scroll past
   record number 65,537. Drag the thumbtrack to the bottom of the vertical
   scrollbar on each grid, and note that the thumbtrack jumps to the top of the
   recordset when released at the bottom.

(c) Microsoft Corporation 2000, All Rights Reserved.
Contributions by Robert Pajaro, Microsoft Corporation


REFERENCES
==========

NOTE: In Visual Basic 6.0 versions prior to SP3, the Hierarchical Flex Grid was
limited to 2048 rows. See the following Knowledge Base article for more
information:

   Q194653 FIX: MSHFLexGrid Does Not Display More Than 2048 Rows

Additional query words:

======================================================================
Keywords          : kbDatabase kbDataBinding kbVBp600 kbVBp600bug kbGrpDSVBDB kbGrpDSMDAC kbDSupport kbMDACNoSweep kbATM 
Technology        : kbVBSearch kbAudDeveloper kbZNotKeyword6 kbZNotKeyword2 kbVB600Search kbVB600
Version           : :2.0,2.1 SP2,2.5,2.6,6.0
Issue type        : kbprb

=============================================================================

THE INFORMATION PROVIDED IN THE MICROSOFT KNOWLEDGE BASE IS
PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND.  MICROSOFT DISCLAIMS
ALL WARRANTIES, EITHER EXPRESS OR IMPLIED, INCLUDING THE WARRANTIES
OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.  IN NO
EVENT SHALL MICROSOFT CORPORATION OR ITS SUPPLIERS BE LIABLE FOR
ANY DAMAGES WHATSOEVER INCLUDING DIRECT, INDIRECT, INCIDENTAL,
CONSEQUENTIAL, LOSS OF BUSINESS PROFITS OR SPECIAL DAMAGES, EVEN IF
MICROSOFT CORPORATION OR ITS SUPPLIERS HAVE BEEN ADVISED OF THE
POSSIBILITY OF SUCH DAMAGES.  SOME STATES DO NOT ALLOW THE EXCLUSION
OR LIMITATION OF LIABILITY FOR CONSEQUENTIAL OR INCIDENTAL DAMAGES
SO THE FOREGOING LIMITATION MAY NOT APPLY.

Copyright Microsoft Corporation 2001.