C# System.String parameter passed into an unmanaged C++ DLL

[thumperj]

Lost..... How do I call an unmanaged C++ DLL class member function from C# code? I can change any and all of these definitions. I just need to get a string from the C# world to the C++ world without pulling out the rest of my hair.

Using VS 2008

Unmanaged C++ Code in a DLL:
class MyClass
{
public:
bool Foo( char* str);
}

C# code that won't compile:

System.String test = "Hi there!";
MyClass c = new MyClass();
c.Foo( test );