CAPE-OPEN standard is defined as a series of interfaces described in a formal documentation set. They are based on universally recognized software technologies developed in the nineties, such as COM and CORBA. Version 1.0 of CAPE-OPEN specifications is implemented in COM (Component Object Model by Microsoft). In the last years, Microsoft has designed and developed a new specification for interoperability among different platform for implementing ‘cross platform software', namely .NET. The .NET framework is definitely a step forward into interoperable and easy-to-develop applications. Since .NET is the evolution of COM technology, it allows the execution of COM codes and the integration of COM code and native .NET code. COM interoperability is the fundamental runtime functionality that allows traditional COM applications using components developed with .NET languages. In this paper we present the design and the implementation of a software layer developed in .NET framework with C#. This software layer talks with the standard CAPE-OPEN COM interfaces, but allow a much more efficient development of codes for the process engineers using standard .NET environment. All this, without modifying the CAPE-OPEN standard interfaces included into most process simulation software available in the market today. With the proposed framework it is possible to develop cape open unit operation and thermodynamic models in a much simpler and self-evident way making it easier for non specialist to write the CO necessary code. Examples are reported of unit operations and thermodynamic property modules developed in the new framework.