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Q304267: FIX: Error in VBA6.DLL When Concatenating ADO Recordset Field

Article: Q304267
Product(s): Microsoft Visual Basic for Windows
Version(s): 2.6,2.6 SP1,6.0
Operating System(s): 
Keyword(s): kbVBp600bug kbVBp600fix kbGrpDSVBDB kbGrpDSMDAC kbDSupport
Last Modified: 24-AUG-2001

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The information in this article applies to:

- Microsoft Visual Basic Enterprise Edition for Windows, version 6.0, used with:
   - Microsoft Data Access Components versions 2.6, 2.6 SP1, 2.7 
- Microsoft Visual Basic Professional Edition for Windows, version 6.0, used with:
   - Microsoft Data Access Components versions 2.6, 2.6 SP1, 2.7 
- Microsoft Visual Basic Learning Edition for Windows, version 6.0, used with:
   - Microsoft Data Access Components versions 2.6, 2.6 SP1, 2.7 
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SYMPTOMS
========

If you reference a field value in an ActiveX Data Objects (ADO) recordset when
BOF or EOF is true, if you use late binding, and if you concatenate it to a
string, an unhandled exception occurs in VBA6.DLL and causes an error.

Under Windows 95 or Windows 98, you receive the following error message:

  VB6 Has Caused An Error in VBA6.DLL

Under Windows NT 4.0, you receive the following Dr. Watson error:

  An application error has occurred and an application error log is being
  generated. VB6.EXE. Exception: access violation (0xc0000005) address
  0x0fa91abd

Under Windows 2000, Visual Basic quits.

CAUSE
=====

If you pass a reference to an ADO field value when BOF or EOF is true, the
following error message normally appears:

  Either BOF or EOF is true, or the current record has been deleted. Requested
  operation requires a current record.

However, if you reference a field value in an ADO recordset when BOF or EOF is
true, if you use late binding, and if you concatenate it to a string, an
unhandled exception occurs in VBA6.DLL and causes the above-mentioned error
messages.

STATUS
======

Microsoft has confirmed this to be a bug in the Microsoft products listed at the
beginning of this article. This bug was corrected in Visual Basic 6.0 Service
Pack 3.

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

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

1. Open a new Standard EXE project in Visual Basic. Form1 is created by default.

2. Place a command button on Form1.

3. Add the following code to the button's click event:

    Dim strConn As String
    Dim strSQL As String
    
    strConn = "provider=sqloledb;data source=stevenbr01;initial catalog=northwind;user id=sa;"
    strSQL = "SELECT * FROM Customers"
    
    Set cn = CreateObject("ADODB.Connection")
    Set rs = CreateObject("ADODB.Recordset")
    
    cn.Open strConn
    
    rs.CursorLocation = 3
    rs.Open strSQL, cn, 1, 1
    
    While Not rs.EOF
      For i = 0 To rs.fields.Count - 1
        If Not IsNull(rs.fields(i).Value) Then
          Debug.Print rs.fields(i).Value & ""
        End If
      Next
      rs.movenext
    Wend
     
    Debug.Print "value " & rs.fields("contactname") '<this fails
    'Debug.Print rs.fields("contactname") '<this works

4. Modify the ADO connection string in the strConn variable as appropriate for
  your environment.

5. Run the project, and click the command button. Notice that data scrolls by in
  the Immediate window. When the recordset is fully read, you receive the
  above-mentioned error messages.

6. To see the error that should occur under these circumstances, comment the
  first Debug.Print line and uncomment the second one, which does not
  concatenate the field value to the word "value " in the print statement.
  Then, rerun the project.


Additional query words: VBA6.dll

======================================================================
Keywords          : kbVBp600bug kbVBp600fix kbGrpDSVBDB kbGrpDSMDAC kbDSupport 
Technology        : kbVBSearch kbAudDeveloper kbZNotKeyword6 kbZNotKeyword2
Version           : :2.6,2.6 SP1,6.0
Issue type        : kbbug
Solution Type     : kbfix

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