Spell-Checking Dialog Boxes
When you call the CheckControlAsync method, SpellChecker for Silverlight displays a dialog box that highlights each of the errors found in the control and allows the user to correct or ignore each error.
SpellChecker for Silverlight contains a built-in spell dialog box that is used by default. You can use the built-in dialog box as-is, customize it, or replace it with your own custom version.