ADO: Recordcount return -1

Error : Recordcount May Return -1 while using ADO connection

The problem is ADO defaults to a Server side cursor. You can only use the RecordCount property with a Client side Cursor.

Do something like...
rsMyRecordset.CursorLocation = adUseClient

If I may guess, the reason the RecordCount doesn't work in your code is that the default cursortype, adOpenForwardOnly, of the recordset doesn't support it. ForwardOnly recordsets ("firehose cursors") are very fast when you just want to run through them from top to bottom. So, if you are using adOpenForwardOnly for the cursorType, you may have to change it.

Here's the code:

rs.CursorLocation = adUseClient
rs.Open sql, con, adOpenKeyset, adLockPessimistic