Red squiggly line does not disappear - RapidSpell WPF - Forum

When I tried to hide (Visibility.Collapsed) the WPF textbox or richtextbox, the red squiggly line still displays on the form. I tried to remove the textbox by calling RemoveTextComponent(), but the squiggly line still exists. If I called ClearAllHighlights(), all the squiggly lines for other visible textboxes are also removed. How do I clear the squiggly line for a single collapsed textbox? Thanks.