The right way to use Globals Constants

Question

In almost every project, I can't decide on how to deal with certain global constant values. In the older days, when I wrote C++ programs which didn't used dll's, it was easy. Just create and .h file with a number of const that described certain constant values for my project. Then I had every file include it, and ta-da! It worked. Clean, respected the DRY principle and was simple.

Now my projects are C# .Net, which gives me a large range of options to deal with this problem. From what I know:

1. Create an Assembly whose only purpose is to hold constant values for my project. Every other Assembly should then reference this one. I respect DRY and KISS, since adding references is simple enough. Main problem here is that I'd need to recompile the whole source to update those values.

2. Use a app.config file and have all other Assemblies retrieve the constant during initialization. So I add the overhead of having to initialize everything just to access a global value. Is more flexible but also more painful.

3. Use resources. I think it's the same as with app.config.

So, I know there's a better way to do this constants declaration. But I don't know and, so far, have been unable to find how to do it. Can you please help? I have candy!

Thanks all

Answer 1

Try to avoid the God class and static 'helper' classes if you can help it. You should try your best to move the constant data into the appropriate classes.

I'm assuming that since you are using C# you want to develop with proper object oriented designs, principles, and patterns. Remember, objects are about behavior --not necessarily functionality. In my opinion, thinking functionally leads to producing procedural code.

You can use the Singleton pattern when the data is used throughout many objects. Although, it's not necessarily a best practice. Lately, I've started using IoC dependency injection more in these situations with Unity and MEF.

Answer 2

If you want the values to be capable of being changed at runtime, use app.config.

If you want them to be fixed at runtime then you're going to have to (and want to, to stop users messing around with them) recompile every time you want to change them, so use whatever's appropriate for your language. In the case of C#, some kind of GlobalValues class/assembly.

Don't use a resource file for global values or settings unless you want to swap sets of values in and out as a group (e.g. when compiling for a different language).

Answer 3

compile time constants vary with the universe in which you inhabit. So pi and e are compile time constants.

runtime constants could potentially vary with each new version.

settings could potentially vary each new time an application is run (or more often depending on how settings are implemented, i.e. db drive, config file driven, etc).