Hi,

There are many ways: for managed C++ see #using directive.

To use C# class from unamanged world, register it by regasm utility [1], and
treat it as usual COM object. Or create custom CLR host and load this class
[2] or simply call ClrCreateManagedInstance API.

[1] "Calling a .NET Component from a COM Component"
http://msdn.microsoft.com/library/en-us/dndotnet/html/callnetfrcom.asp

[2] "Microsoft .NET: Implement a Custom Common Language Runtime Host for
Your Managed App"
http://msdn.microsoft.com/msdnmag/issues/01/03/clr/clr.asp

..
Regards,
Vadim.