Neil,

>The problem is that when I use free fpw26 tables in the same example, I receive the following error. And... it does not look good for saving data back to free tables. Any suggestions? Do I have to create a Custom Data Access Class?

It looks like you're running into the limitation with the VFP OLE DB provider mentioned in the Dev Guide topic "Does the VFP OLE DB Provider work with free tables?":

The Visual FoxPro OLE DB Provider works with both database and free FoxPro tables (including FoxPro 2.6 tables), however support is limited where there is no database container. ADO.NET cannot retrieve sufficient schema information such as the primary key required for the Command Builder for many automatic operations. This means you need to create custom data access classes when working with free tables (see the Help topic Creating Custom Data Access Classes for details). In addition, depending on file locations it may be necessary to specifically path operations (for example: Update c:\data\customers).

Regards,