First of all great work on this library!
Id like to make a suggestion.
I am having an issue intergrating the library with my code. I store passwords as SecureString but classes such as SevenZipExtractor passes around passwords as insecure string types so I'm having to convert from SecureString to string
to use the library. I'm not sure why passwords are not stored in SevenZipSharp as SecureString (perhaps for platform compability) but It would be nice if the library supported them and in turn was more secure.