Vista - Exporting Managed Code as Flat API to Unmanaged World

Hi,

I have a MC++dll, whose functions i want to use in unmanaged c++. I
read that one of the ways to use the managed

functions in unmanaged world is by exposing the managed api as flat
api.
I tried that and with simple data types it worked. But now i need to
export a function which needs to take a gc

struct as parameter, and then fill some values in it, and then the
unmanaged c++ will use that info.

Here's what i did

//My gc struct
[StructLayout(LayoutKind::Sequential,CharSet=CharSet::Ansi)]
public __gc struct STLayout {
public:
[MarshalAs(UnmanagedType::LPTStr)]
String* ID;
};
//End

Now i'm trying to export this through a funtion like this:-

__declspec(dllexport) int
ExportL([MarshalAs(UnmanagedType::Struct)]STLayout*& Layout)

And when i compile this dll. i'm getting the following error:-

error C3395: __declspec(dllexport) cannot be applied to a function
with the __clrcall calling convention

Now im stuck....
what i dont understand is that

1) why isn't the MarshalAs attribute working here.....
2) What is the preferred way of exporting the managed types to c+
+....other than the COM interop, mixed-mode

solutions......

Any other ideas...

Thanks in advance...
Saad.