PRB: Most ADO Recordset Properties Are Not Marshalled

• ActiveX Data Objects (ADO), versions 1.5, 2.0, 2.1 SP2

SYMPTOMS

Most ActiveX Data Objects (ADO) Recordset properties such as STATUS and SOURCE are not marshalled between processes. In ADO 1.5, only a couple of underlying OLE DB properties of the rowset get marshalled with the rowset; DBPROP_IRowsetChange and DBPROP_IRowsetUpdate. When passing a recordset between processes, you primarily get the recordset data without any state.

In the case of the STATUS property, it should be noted that error based status codes originating from operations such as UPDATE, UPDATEBATCH, and so forth, are not preserved. Only the data is preserved.

The SOURCE property will be null when marshalling a recordset irrespective of what is set at the server.

RESOLUTION

You must return the Recordset state data, such as SOURCE and STATUS properties, explicitly in your own data structures. For example, if you call a method of a business object that returns a recordset, you would also create an argument of the method that can be used to return the state data.

STATUS

This behavior is by design.

MORE INFORMATION

Steps to Reproduce Behavior

1. Write an OLE Out-of-process server (ActiveX EXE)in Visual Basic (VB) and add a method returning an ADO disconnected recordset and a method that updates the recordset. Before returning the recordset from the method, use another recordset object to modify one of the records held in the first recordset:




   ' Function to return a disconnected recordset.
   Public Function GetRcdSet() As Recordset

   Dim con As New Connection
   Dim rs1 As New Recordset, rs2 As New Recordset
   Dim newValue as String
   newValue = "Test Modified String"

   On Error GoTo ErrHandler

   con.Open "DSN=SQLServer;database=pubs", "sa"
   Set rs1.ActiveConnection = con
   rs1.CursorLocation = adUseClient

   ' Table1 is a table with the first column Varchar(255).
   rs1.Open "table1", , adOpenKeyset, adLockOptimistic, adCmdTable

   ' Check the value of Source property - should be "Table1".
   Debug.Print rs1.Source
   ' Disconnect recordset.
   Set rs1.ActiveConnection = Nothing

   Set GetRcdSet = rs1

   ' Modify one of the records.
   rs2.Open "table1", con, adOpenDynamic, adLockOptimistic, adCmdTable
   rs2.MoveFirst
   rs2.Fields(0).Value = newValue
   rs2.Update
   rs2.Close
   Set rs2 = Nothing

   con.Close
   Set con = Nothing
   Exit Function

   ErrHandler:
     MsgBox Err.Description

   End Function

   ' Function to update the changes made to the recordset and
   ' also returns the recordset back to the client.
   Public Function Update(rs As Recordset) As Recordset
   Dim con As New Connection

   On Error GoTo ErrHandler

   con.Open "dsn=Ram;database=pubs", "sa"

   Set rs.ActiveConnection = con

   rs.UpdateBatch adAffectAll

   Set Update = rs
   Set con = Nothing
   Exit Function

   ErrHandler:
    MsgBox "Error in updating ErrDesc: " & Err.Description
    Set Update = rs
    Debug.Print "status at server is " & rs.Status
    Set con = Nothing

   End Function 

2. Write a client application (Standard EXE) in VB. In the client application, create the server object, get the disconnected recordset by calling the first method (GetRcdSet) and then modify the first record. Pass the recordset back to the second method of the server (Update) that tries to update the recordset by calling UpdateBatch().
   
   The STATUS property will be 2050 error (modified and concurrency problem) as expected.
   
   Now, check the STATUS property of the recordset returned by the Update method of the server. The STATUS property of the returned recordset is 2 (modified) instead of 2050 (modified and concurrency):


Sample Code

   Private Sub Command1_Click()
      Dim rs As Recordset
      Dim x As Object
      Dim rs2 As Recordset

      Set x = CreateObject("myproj.cls1")
      Set rs = x.GetRcdSet

      ' Check the value of Source property.
      ' Source property is empty string here.
      Debug.Print rs.Source

      rs.MoveFirst
      ' Modify a field in a recordset.
      rs.Fields(0).Value = "String modified at client"

      Set rs2 = x.Update(rs)

      Debug.Print "Status at client" & rs2.Status
      Set rs2 = Nothing
     End Sub 

Additional query words:

Keywords : kbADO150 kbDatabase kbOLEDB kbVBp600 kbGrpVBDB kbGrpMDAC kbDSupport kbMDAC200 kbMDAC210SP2
Version : WINDOWS:1.5,2.0,2.1 SP2
Platform : WINDOWS
Issue type : kbprb