How do you use C++ files and classes in a C# program?

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I'm in a bit of a jam here and need some help. I've got a C++ text economic space game that I wrote a while back and I now need to create a C# version of it with graphics and stuff. But I do not know enough C# yet to completely rewrite it. But someone had told me that there is a way to use C++ files and classes in a C# program, and that that would solve my problem until I learned enough to completely rewrite them in C#. But this friend never told me how exactly to do that. Could someone here please help me or give me some good suggestions? I would sure appreciate it, thanks.

Oh, and by the way, I'm using Microsoft Visual Studio 2008 and it's .net versions of C++ and C#.