What C# collection should I use for this use case?

Question

http://www.dreamincode.net/forums/user/335389-sergio-tapia/

I'm the Helper group, currently there are other groups. I want to write all possible groups to a C# class or something and then in the future when other groups are created I'd just modify that "collection of groups".

My question is, what C# structure should I use for this use case?

Edit: Changed the question and some of the body for clarity.

Answer 1

Changing enumerations is fraught, but can be done to a limited extent. Consider:

public enum SomeColors
{
  Black,
  blue,
  red
}

Code in another assembly compiled to use SomeColors.blue will break if we do:

public enum SomeColors
{
  Black,
  Green,
  blue,
  red
}

Because it will have the value 1 compiled into it, which is now the value of SomeColors.Green while SomeColors.blue is now 2.

Also, if we were to change the first to have the same capitalisation throughout to:

public enum SomeColors
{
  Black,
  Blue,
  Red
}

Then running code would still work, but re-compiling would have compiler errors, as SomeColors.Blue would not work. Also, Enum.Parse would (in this case, depending on the case-sensitivity setting) work depending on which version of SomeColors was available to the running code.

However, adding values is not a breaking change. If we took the first and changed it to:

public enum SomeColors
{
  Black,
  blue,
  red,
  green
}

Then all existing code would be okay, but of course not know about green unless found with Enum.Parse.

So, if you are only going to add, and if you can depend upon nobody trying to Enum.Parse a string from a more recent version, then it'll work.

The same holds true of const values.

If you need to have values be changeable with versions, then you should use:

public static class SomeColors
{
  public static readonly int Black = 0;
  public static readonly int Blue = 1;
  public static readonly int Red = 2;
}

As these are not constants, but fields assigned statically, they will be used from the class rather than compiled-in, and changes to the class will change what is used. Further safety in some cases can be given by making them properties rather than fields; most notably in that if you may want to make the calculated properties in the future, it would be a breaking change if they are currently fields but not if they are already properties.

If you want the values to be dynamic at runtime, then you need a class with an indexer that takes a string and returns an integer.