While surfing the web for different CMIS implementations I found NCMIS. Oh no, NCMIS has nothing to do with NCIS (Navy CIS). NCMIS is a .NET implementation of CMIS.

This version is in an early stage. There is no download available at the moment.

Anybody who wants to contribute to NCMIS can contact the lead developer Allan Thraen at http://ncmis.codeplex.com/