Importing C++ enumerations into C#

Question

I'm currently working on creating a new C# project that needs to interact with an older C++ application. There is an error enumeration that already exists in the C++ app that I need to use in the C# app.

I don't want to just re declare the enumeration in C# because that could cause sync issues down the line if the files aren't updated together.

All that being said my question is this: Is there a way for me to taken an enumeration declared like so:

typedef enum
{
    eDEVICEINT_ERR_FATAL = 0x10001
    ...
} eDeviceIntErrCodes;

and use it in a C# program like so:

eDeviceIntErrCodes.eDEVICEINT_ERR_FATAL

Answer 1

In C/C++ you can #include a .cs file which contains the enumeration definition. Careful use of preprocessor directives takes care of the syntax differences between C# and C.

Example:

#if CSharp
namespace MyNamespace.SharedEnumerations
{
public
#endif


enum MyFirstEnumeration
{
    Autodetect = -1,
    Windows2000,
    WindowsXP,
    WindowsVista,
    OSX,
    Linux,

    // Count must be last entry - is used to determine number of items in the enum
    Count
};
#if CSharp
public 
#endif

enum MessageLevel
{
    None,           // Message is ignored
    InfoMessage,    // Message is written to info port.
    InfoWarning,    // Message is written to info port and warning is issued
    Popup           // User is alerted to the message
};

#if CSharp
    public delegate void MessageEventHandler(MessageLevel level, string message);
}
#endif

In your C# project, set a conditional compilation symbol "CSharp", make sure no such preprocessor definition exists in the C/C++ build environment.

Note that this will only ensure both parts are syncronised at build time. If you mix-and-match binaries from different builds, the guarantee fails.

Answer 2

Check out the PInvoke Interop Assistant tool http://www.codeplex.com/clrinterop/Release/ProjectReleases.aspx?ReleaseId=14120. Its a useful tool for generating PInvoke signatures for native methods.

If I feed it your enum it generates this code. There is a command line version of the tool included so you could potentially build an automated process to keep the C# definition of the enum up to date whenever the C++ version changes.

    public enum eDeviceIntErrCodes 
    {
        /// eDEVICEINT_ERR_FATAL -> 0x10001
        eDEVICEINT_ERR_FATAL = 65537,
    }

Answer 3

Simple answer is going to be no. Sorry, you are going to have to re-declare.

I have, in the past however, written scripts to import my C++ enums to a C# format in a enums.cs file and run it as part of the build, that way everything syncs.