All formats

CB7 libraries for C#

SharpCompress reads 7z in pure managed code (LZMA, LZMA2, BZip2, PPMd, encrypted archives) through the same ArchiveFactory.OpenArchive call it uses for CBZ, CBR and CBT. It also writes 7z (SevenZipWriterOptions). MIT license.

For 7-Zip’s own engine, wrappers around the native 7z.dll exist (Squid-Box.SevenZipSharp), but they need the 7-Zip library shipped with your app.