System.Text.StringBuilder supportedCharacters = new System.Text.StringBuilder();
 string languageName = "French";
 FREngine.ITextLanguage textLanguage = engineLoader.Engine.PredefinedLanguages.Find(languageName).TextLanguage;
 foreach (FREngine.IBaseLanguage baseLanguage in textLanguage.BaseLanguages) {
 supportedCharacters.AppendFormat("Alphabet letters: {0}\n", baseLanguage.LetterSet[FREngine.BaseLanguageLetterSetEnum.BLLS_Alphabet]);
 supportedCharacters.AppendFormat("Prefixes: {0}\n", baseLanguage.LetterSet[FREngine.BaseLanguageLetterSetEnum.BLLS_Prefixes]);
 supportedCharacters.AppendFormat("Suffixes: {0}\n", baseLanguage.LetterSet[FREngine.BaseLanguageLetterSetEnum.BLLS_Suffixes]);
 }
 supportedCharacters.AppendFormat("Punctuation marks: {0}\n", textLanguage.LetterSet[FREngine.TextLanguageLetterSetEnum.TLLS_InterwordPunctuators], textLanguage.LetterSet[FREngine.TextLanguageLetterSetEnum.TLLS_Prefixes], textLanguage.LetterSet[FREngine.TextLanguageLetterSetEnum.TLLS_Suffixes]);
 MessageBox.Show(supportedCharacters.ToString());

Sample output for English:

Alphabet letters: '-.ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz’
Prefixes: "'(-.[{©—‘’“•■□▲△►▻▼▽◄◅◊◎◦★☆♦✓❖
Suffixes: !"')*,-.:;?]}©®—’”™
Punctuation marks: !"#$%&'()*+,-./:;<=>?[]_{}£¥§©«°»—’“”„•€■□▲△►▻▼▽◄◅◊◎◦★☆♦✓❖

Sample output for French (please note symbols added: ÀÂÆÇÈÉÊËÎÏÔÙÛÜàâæçèéêëîïôùûüÿŒœŸ)

Alphabet letters: '-.ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyzÀÂÆÇÈÉÊËÎÏÔÙÛÜàâæçèéêëîïôùûüÿŒœŸ’
Prefixes: "'(-.[{©«—‘“•■□▲△►▻▼▽◄◅◊◎◦★☆♦✓❖
Suffixes: !"')*,-.:;?]}©®»—’”™
Punctuation marks: !"#$%&'()*+,-./:;<=>?[]_{}£¥§©«°»—’“”„•€■□▲△►▻▼▽◄◅◊◎◦★☆♦✓❖