Here are the instructions demonstrating how to create a custom TDF dictionary using the Dictionary Configuration project.
See whether the needed dictionary exists on the following site: Dictionaries or create a text file following the "word-per-line" rule. You should exclude any special symbols after each word for example: test/SDG or test::. The correct syntax is test
Save the text file with Unicode (UTF-8 with signature) encoding
Rename the .dic / .txt extension to .tdf
Convert the file by using the Dictionary Configurator tool.
Place the new dictionary in the "\RadControls\Spell\TDF" folder of the Dictionary Configuration project, test and verify that the spellchecker works properly with it.If the dictionary language is incompatible with the phonetic spell check provider then set the spellchecker to use its EditDistanceProvider (SpellCheckProvider="EditDistanceProvider").