BUG: RDO Rowcount May Be Wrong When Using rdAsyncEnable Flag

• Enterprise Edition of Microsoft Visual Basic for Windows, 32-bit only, version 4.0

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:

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

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