Currently, search-as-you-type functionality is supported only for RadGridView. And for the time being, it is not scheduled for implementation for RadTreeListView. Our main concern is that this feature can be applied only on the parent items since the children are not always available and the control knows basically only for the parent items. The same is the case with filtering. Thus, the behavior for searching would have seemed incomplete and not fully functional.
I do hope you understand our concern.
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and share your thoughts.