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How To Implement Visual Basic COM Objects Returning Recordsets

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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.
-or-
Type Mismatch
-or-
error 'ASP 0115' - A trappable error occured in an external object

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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:

    Note You must change the UID and the PWD values to the ones that are used on your system.
    Public Function TestRs() as ADODB.Recordset
       Dim rsObj As ADODB.Recordset
       Dim cnObj As ADODB.Connection    

       set rsObj = New ADODB.Recordset         
       set cnObj = New ADODB.Connection

       'Open connection to database
       cnObj.Open("DSN=pubs;uid=<username>;pwd=<strong password>")
       
       'To use disconnected Recordset you must use client side cursors
       rsObj.CursorLocation = adUseClient

       rsObj.Open "select * from authors", cnObj, adOpenKeyset, _
          adLockOptimistic, adCmdText
       
       'Disconnected recordset
       Set rsObj.ActiveConnection = Nothing

       'Set return value
       Set Testrs = rsObj
       
       'Clean up resources
       cnObj.Close
       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
   %>

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References

For additional information, click the following article number to view the article in the Microsoft Knowledge Base:
244012 INFO: Type Mismatch Errors When You Pass Parameters from ASP to a Visual Basic Component

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Keywords: kbcodesnippet, kbdatabase, kberrmsg, kbhowto, KB224424

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Article Info
Article ID : 224424
Revision : 6
Created on : 7/1/2004
Published on : 7/1/2004
Exists online : False
Views : 698