Combing C# and C++

[TnGraham]

Hey,
I am working on this prject that is in C++ using MFC for GUI, but now we are trying to use WPF for the GUI which uses C#. With this in mind, I want to know how do you interact with C++ through C#. If anyone can give a brief example or point me to a good site that speaks on ths subject. Thanks for any help!!