I created a CompletionSession and set its filter properties:
session.CanFilterUnmatchedItems = true; session.MatchOptions = CompletionMatchOptions.UseShorthand;
Then I added 3000 CompletionItems to this session.
After opening CompletionSession, my input can trigger list filtering. However, if there are still many filter list items at this time, there will be a freeze during the input process.
This happens only when the CanFilterUnmatchedItems property is set to'true'.
So I speculate that in the case of too many Items, there should be some performance problems in filtering.