RadGRidView can only select items that are in view - items that are passing the filters. I guess the problem with Select All is caused by the fact that you iterate the original item collection which contains all items. You could resolve the problem by iterating over the Items collection of the grid which
only contains the visible items.
All the best,
the Telerik team
Do you want to have your say when we set our development plans?
Do you want to know when a feature you care about is added or when a bug fixed?
Telerik Public Issue Tracking
system and vote to affect the priority of the items