Optional: If true, the search string is spellchecked and spellcheck suggestions are included in the search. Spellchecking is carried out according to the specified SearchLanguage, controlling the set of phonetic and language-specific rules used, and the dictionaries spellchecked against. Default value: false

public Nullable<bool> SpellcheckSearchString { get; set; }

public Nullable<bool> SpellcheckSearchString { get; set; }