How to Pass unmanaged struct C++ object to C# delegates. And how to return that object from C# through C++ function pointer using delegates

I have Managed.dll written in C# and Unmaanaged.exe written in C++.

Trying to pass C++ function pointer and C++ obect to C#(com dll), 

Invoke / call this funtion pointer in C# and pass C++ object after  populating from C#.

Regards,

Lokesh