I have a RadListBox that I am loading about 3000 items into. I am using a CollectionViewSource so that I can group on a certain attribute of the object. It takes like a minute to load the items into the Listbox. I know it takes a hit with the grouping. Is there anything I can do to speed it up? Does RadListbox virtualization get turned off on grouping just like the Microsoft control? Because even after things are loaded, just scrolling up and down is slow. The who control doesn't run well.