Q151815: BUG: RDO Rowcount May Be Wrong When Using rdAsyncEnable Flag

Article: Q151815
Product(s): Microsoft Visual Basic for Windows
Version(s): 4.00 | 4.00
Operating System(s): 
Keyword(s): kbDatabase kbODBCkbbuglist
Last Modified: 18-FEB-2000

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The information in this article applies to:

- Microsoft Visual Basic Enterprise Edition, 32-bit, for Windows, version 4.0 
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SYMPTOMS
========

When using rdoResultsets, the RowCount property is useful for determining how
many records have been returned by the query. Depending on the driver and data
source, the RowCount property returns either -1 to indicate that the number of
rows is not available, or 0 to indicate that no rows were returned by the
rdoResultset. If the driver is capable of returning a row count, the RowCount
property returns the number of rows in the rdoResultset.

When opening an rdoResultset using the rdAsyncEnable flag, the RowCount will
always return 0. This could lead to the mistaken assumption that the query
returned no records.

WORKAROUND
==========

If a Movelast is executed against the rdResultset before the RowCount is
queried, then the RowCount will be correctly set.

If the rdAsyncEnable flag is not passed to OpenResultset, the problem does not
occur.

STATUS
======

Microsoft has confirmed this to be an issue in the Microsoft products listed at
the beginning of this article. Microsoft is researching this issue and will post
new information here in the Microsoft Knowledge Base as it becomes available.

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

The following Visual Basic code opens a connection to the server and creates an
asynchronous rdoResultset. This code uses a "DSN-less" ODBC connection so you do
not need to set up a DSN (Data Source Name) with the ODBC Admin utility.

For more details on doing this DSN-less connection, see the following article in
the Microsoft Knowledge Base:

  Q147875 : How to Use DSN-Less ODBC Connections with RDO and DAO

In the following code, MyServer is assumed to be a Microsoft SQL Server with the
default database PUBS installed.

Steps to Reproduce Problem
--------------------------

1. Start the 32-bit Edition of Visual Basic version 4.0 for Windows. Form1 is
  created by default.

2. Add a single Command button to the form.

3. Add the following code to the Command1 Click Event:

     Private Sub Command1_Click()
     Dim rdoConn As rdoConnection
     Dim rdoRes As rdoResultset
     Dim tempStr As String

         Set rdoConn = rdoEnvironments(0).OpenConnection("", _
                                      rdDriverNoPrompt, _
                                      False, "DRIVER={SQL Server};" & _
                                      "SERVER=MySQLServer;DATABASE=pubs;" & _
                                      "UID=sa;PWD=;")

        Set rdoRes = rdoConn.OpenResultset("select * from authors", _
                                           rdOpenKeyset, rdConcurLock, _
                                           rdAsyncEnable)

        While rdoRes.StillExecuting
          DoEvents
        Wend
        Debug.Print rdoRes.RowCount
        rdoRes.Close
        rdoConn.Close

     End Sub

4. From the File menu, select Save.

5. Press the F5 key, or click Start on the Run menu to run the application.
  Click on Command1 and note that in the debug window the number 0 appears.

REFERENCES
==========

Visual Basic Online Help OpenResultset, RowCount

Additional query words: 4.00 vb4win vb432

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Keywords          : kbDatabase kbODBC kbbuglist
Technology        : kbVBSearch kbAudDeveloper kbVB400Search kbVB400
Version           : 4.00 | 4.00
Issue type        : kbbug

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