Xceed Encryption Library does not support Salt natively but is very easy to do. In an utopian world, salting would not be necessary. Every user would choose strong pass phrase that could withstand dictionnary attacks. But, needless to say, we do not live in this perfect world. This is why salt was invented. Salting simply consist of prepending or appending a random number to the pass phrase before calling SetSecretKeyFromPassphrase.
SetSecretKeyFromPassPhrase( STR( S ) | PS )
S is the salt number,
STR is your favorite langage string conversion function and
PS is the passphrase.