ComponentOne SpellChecker for WinForms is sold as part of ComponentOne Studio Enterprise and the ComponentOne Studio for WinForms.

C1Spell Component
The C1Spell component features a built-in dialog box, the ability to generate alternate spelling for suspect words, create new main dictionaries based on existing main dictionaries (such as those created in Microsoft Word), and ignore or change all suspect words.

Building and maintaining dictionary files - ComponentOne SpellChecker for WinForms...