Returning a structure from C# to PB 12.5

We have written some C# code that calls a web service that returns a complex datatype to the C# just fine.  What do I create in C# that will be returned as a simple PB structure?  Is there a special way to declare it in C#? The DLL is com-callable and the functions work fine if the return datatype is a simple one.

Thanks,

Tom (& Mike)