Currently, within the LoadItems() method the items are being iterated directly, thus a second query to the database is triggered.  A separate list for this operation should be created.

When tabbing in grouped RadGridView placed in Grid with another visual element inside it, GroupRenderMode is set to Flat  and second group is not in ViewPort, selected row changed its state to Unfocused.

Add a property to control GridView ControlPanelItem visibility.

Respect IVirtualizedItemProvider for items of RadGridView . 

Implement Excel-like horizontal locked scrolling. Clicking on the scrollbar should scroll into view the first column that is not visible at the moment, i.e. all visible columns should be moved out of the viewport.