libmono-windowsbase3.0-cil 2.6.7-5ubuntu2 (i386 binary) in ubuntu natty

 Mono is a platform for running and developing applications based on the
 ECMA/ISO Standards. Mono is an open source effort led by Novell.
 Mono provides a complete CLR (Common Language Runtime) including compiler and
 runtime, which can produce and execute CIL (Common Intermediate Language)
 bytecode (aka assemblies), and a class library.
 .
 This package contains the WindowsBase library for CLI 2.0 which provides
 the System.IO.Packaging namespace.