PRB: ADO: Recordcount May Return -1

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Symptoms

When you request the RecordCount for a serverside recordset, a -1 may return. This occurs with ActiveX Data Objects (ADO) version 2.0 or later when the CursorType is adOpenForwardonly or adOpenDynamic. This occurs with ADO 1.5 only when the cursortype is adOpenForwardonly. Testing with the OLEDB provider for JET and SQL Server produces varying results, depending on the provider.


Providers may not support some CursorTypes. When you select a CursorType that is not supported, the provider should select the CursorType closest to what you request. Please refer to the documentation that comes with your provider. Also, please note that not all combinations of LockType and CursorType work together. Changing a LockType may force a change in the CursorType. Be sure to use debug to check the value of CursorType when conducting tests with your OLEDB provider.

Cause

The number of records in a dynamic cursor may change. Forward only cursors do not return a RecordCount.

Resolution

Use either adOpenKeyset or adOpenStatic as the CursorType for server side cursors or use a client side cursor. Client side cursors use only adOpenStatic for CursorTypes regardless of which CursorType you select.

Status

This behavior is by design.

More Information

Steps to Reproduce Behavior

  1. Open a standard .exe project in Visual Basic.
  2. From the Project menu, choose References.
  3. Select the Microsoft Active Data Object Library.
  4. Paste the following code in the form code window:
           Option Explicit
    Dim rs As ADODB.Recordset

    Private Sub Form_Load()
    'set up rs
    Set rs = New ADODB.Recordset
    rs.CursorLocation = adUseServer
    rs.Open "Select ProductID from products", & _
    "Provider=Microsoft.Jet.OLEDB.3.51;" & _
    "Data Source=d:\vb5_win95\nwind.mdb", _
    adOpenDynamic, adLockUnspecified

    Debug.Print rs.RecordCount
    End Sub
  5. Replace the preceding Data Source with a Data Source on your computer. Run the preceding form and note the record count. Change the CursorType to adOpenForwardonly and note the record count.
  6. Change the CursorLocation to adUseClient and experiment with the different CursorTypes. In all cases the correct record count returns.

References

ActiveX Data Objects (ADO) Help; search on: "CursorType Property."
Propiedades

Id. de artículo: 194973 - Última revisión: 06/22/2014 - Revisión: 1

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