How do I share a constant between C# and C++ code?

Question

I\'m writing two processes using C# and WCF for one and C++ and WWSAPI for the second. I want to be able to define the address being used for communication between the two

Answer 1

When I've had to do that stuff in the past, I've simply added an extra pre-compilation step to the build process which automagically creates one file from another.

Since your constants will probably be within a class in C#, you can use that as the source file:

MyClass.cs:
    class MyClass {
        public const int NUM_MONTHS = 12;    //COMMON
        public const int YEAR_BASE = 1900;   //COMMON
    }

grep '//COMMON' MyClass.cs
    | sed -e 's/^ *public const [a-z][a-z]*/#define/'
          -e 's/ *= */ /'
          -e 's/;.*$//'
    >MyClass.h
grep '//COMMON' MyClass.cs | sed -e 's/ *public //' -e 's/;.*$/;/' >MyClass.hpp

This will give you:

MyClass.h:
    #define NUM_MONTHS 12
    #define YEAR_BASE 1900

MyClass.hpp:
    const int NUM_MONTHS = 12;
    const int YEAR_BASE = 1900;

Now, getting Visual Studio to perform that step is not something I know how to do. You'll have to investigate whether or not it's even possible. The UNIXy text processing tools are really worth downloading. I have CygWin installed on a few boxes but, for something this localised, you could get away with individual GnuWin32 packages.

You could probably do a similar job in PowerShell but I'm not really well versed in that.

---

Now that's a bit of a kludge so may I suggest a possibly better way for you particular question. Don't use a constant at all. Put the address into a configuration file and have your C# and C++ code read it at startup.

That way, you get to share the value painlessly and it's configurable in case you ever want to change it in future.