One of the HIS Product Team Test Engineers has put together a .NET Managed C++ Extensions Sample for CPI-C that can be used with HIS 2010. Here is an overview of the sample:

This sample is a Visual Studio 2010 Sample project. This project is a .NET Managed C++ extensions for utilizing CPI-C (WinCPIC32) API included with Host Integration Server. The sample code file is a TP program based on the APINGD. In the readme file includes a sample to call this DLL from a .NET Managed C# application/service. Also, exported interfaces for the Native C++ DLL will allow for a .NET application to utilize P/Invoke to call wrapper functions directly.

The sample is available for via the link above. It is also linked on the Host Integration Server Developer Center page.