HOWTO: Implement Visual Basic COM Objects Returning Recordsets

• Active Server Pages
• ActiveX Data Objects (ADO), versions 1.5, 2.0, 2.1 SP2
• Microsoft Visual Basic Learning, Professional, and Enterprise Editions for Windows, versions 5.0, 6.0
• Microsoft Internet Information Server versions 4.0, 5.0

SUMMARY

This article describes, by example, how to implement a Visual Basic Component Object Model (COM) Object that returns a recordset to Active Server Pages (ASP).

Implementing this incorrectly can result in memory leaks or one of the following errors:

The operation requested by the application is not allowed if the object is closed.

Type Mismatch

error 'ASP 0115' - A trappable error occured in an external object

MORE INFORMATION

Use the following steps to implement a method that returns a recordset from a Visual Basic COM Object to Active Server Pages:

1. Create a Visual Basic ActiveX DLL project called PassRsPrj.



2. Add a class module and change its name to PassRsObj.



3. Implement the following method:




Public Function TestRs() as ADODB.Recordset
    Dim rsObj As New ADODB.Recordset
    Dim cnObj As New ADODB.Connection    
      
    cnObj.Open("DSN=pubs;uid=sa;pwd=")
    
    Set rsObj.ActiveConnection = cnObj

    'To use disconnected Recordset you must use client side cursors
    rsObj.CursorLocation = adUseClient

    rsObj.Open "select * from authors"
    
    'Use a disconnected recordset to efficiently use connection pooling
    Set rsObj.ActiveConnection = Nothing

    'Clone the recordset.
     'NOTE You can only clone a recordset that supports bookmarks 
     Set Testrs = rsObj.Clone 
    
    'Clean up Resource
    rsObj.Close
    cnObj.Close
    
    Set rsObj = Nothing
    Set cnObj = Nothing
    
End Function 

4. Create an ASP page with the following code:




<%
Dim rsTest, oTestPassRs

Set oTestPassRs = Server.CreateObject("PassRsPrj.PassRsObj")
Set rsTest = oTestPassRs.TestRs()

Do 
   Response.Write ( "Value in Record = " & rsTest(1) & "<BR>" )
   rsTest.MoveNext
Loop until rsTest.EOF

rsTest.Close
Set rsTest = Nothing
Set oTestPassRs = Nothing
%> 

Additional query words:

Keywords : kberrmsg kbADO kbASP kbCOMt kbDatabase kbVBp kbVBp500 kbVBp600 kbGrpASP kbGrpVBDB kbGrpMDAC kbDSupport kbADO210sp2 kbMDAC210SP2 kbiis400 kbiis500
Version : WINDOWS:1.5,2.0,2.1 SP2,5.0,6.0; winnt:
Platform : WINDOWS winnt
Issue type : kbhowto