Jialiang Ge has just finished a summary of solutions to invoke .NET assembly from native C++ code.

Solution 1. Use a C++/CLI wrapper
Solution 2. Host CLR
Solution 3. Convert .NET assembly to a COM server, and call it from C++ through .NET-COM interop

The detailed and working code samples are attached to the above article. If you have any comments or questions about the code samples, please do contact onecode@microsoft.com. Your feedback is very important to the work.