Note: this is not a pure-managed implementation of a compression library. Quite the opposite -- it's a thin wrapper for the C++ libraries written in the 7-Zip project for decompressing 7z/zip/gzip/bzip2/tar/rar/cab/iso/... etc (and for compressing in 7z,gzip,bzip2,zip,tar,etc)
7zSharp is a .NET 2.0 LGPL wrapper around the 7z LZMA SDK and executable written in C#, providing a library (DLL) wrapper and simplified API to encode and decode using the 7z library.