Is it possible to share an enum declaration between C# and unmanaged C++?

Question

Is there a way to share an enum definition between native (unmanaged) C++ and (managed) C#?

I have the following enum used in completely unmanaged code:

enum MyEnum { myVal1, myVal2 };

Our application sometimes uses a managed component. That C# component gets the enum item values as ints via a managed C++ interop dll (from the native dll). (The interop dll only loads if the C# component is needed.) The C# component has duplicated the enum definition:

public enum MyEnum { myVal1, myVal2 };

Is there a way to eliminate the duplication without turning the native C++ dll into a managed dll?

Answer 1

You can use a single .cs file and share it between both projects. #include in C++ on a .cs file should be no problem.

This would be an example .cs file:

#if !__LINE__    
namespace MyNamespace
{
    public 
#endif

// shared enum for both C, C++ and C#
enum MyEnum { myVal1, myVal2 };

#if !__LINE__
}
#endif

If you want multiple enums in one file, you can do this (although you have to temporarily define public to be nothing for C / C++):

#if __LINE__
#define public
#else
namespace MyNamespace
{
#endif

    public enum MyEnum { MyEnumValue1, MyEnumValue2 };
    public enum MyEnum2 { MyEnum2Value1, MyEnum2Value2 };
    public enum MyEnum3 { MyEnum3Value1, MyEnum3Value2 };

#if __LINE__
#undef public
#else
}
#endif