When using the ResultsGrid.Filter property of the SearchPage class of the dot net API, the results grid is not filtered by the property specified in the code.
When you specify the ResultsGrid.Filter property in your code and then use that search page in the CRM application, the grid is not filtered by the filter you specified.
This has been escalated to our devolpment team to be fixed.
This is currently an issue in 7.2e
The ResultsGrid.Filter property does work for the ListPage class.