PRB: Updating ADO Recordset Persisted from Read-Only Cursor May Fail

When you try to update a persisted ADO recordset from a read-only cursor, the following error appears:

In ADO 2.0 and later, you can use the SAVE method on a recordset object to persist recordsets to local storage and reload them later. For optimization purposes, when a read-only recordset is persisted, ADO does not set the Unique Rows property on the provider. That is, no base table information is persisted. An update error occurs when you try to update a recordset due to lack of base table information.

Before updating a recordset that has been persisted, make sure that it was opened and persisted with attributes that allow updating. See the "More Information" section for sample code.

This behavior is by design.

Steps to Reproduce Behavior

1. Start a new Standard EXE project in Visual Basic. Form1 is created by default.
2. Add a reference to the Microsoft ActiveX Data Objects 2.x Library.
3. Double-click Form1. Copy and paste the following code under the Form_Load() event:

     Dim rs1 As New Recordset
     Dim rs2 As New Recordset
     Dim cn As New Connection
     
     cn.CursorLocation = adUseClient
   
     cn.Open "Provider=SQLOLEDB;Data Source=MyServer;Initial Catalog=Pubs;User ID=sa;Password=;"
     On Error Resume Next
     cn.Execute "Drop Table T1"
        cn.Execute "CREATE TABLE T1 (K1 Int PRIMARY KEY, F2 Int)"
     On Error GoTo 0
     cn.Execute "INSERT INTO T1 VALUES(0, 100)"
     
     rs1.Open "Select K1, F2 From T1", cn, adOpenForwardOnly, adLockReadOnly
   
     'Commenting the above line and uncommenting the next line will not generate the error.
     'rs1.Open "Select K1, F2 From T1", cn, adOpenKeyset, adLockOptimistic
     
     If Dir("Persist.xml") <> "" Then Kill "Persist.xml"
     rs1.Save "Persist.xml", adPersistXML
   
     rs2.Open "Persist.xml", cn, adOpenKeyset, adLockBatchOptimistic, adCmdFile
   
     rs2.AddNew
     rs2("K1") = 1
     rs2("F2") = "200"
     rs2.UpdateBatch  'Error occurs here
   					

4. Run the project and note the error.
5. Modify the code as described in the comments line and re-run the project.