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Don't Use Enumerables as Numbers

I just read another discussion of Enums in .NET where the author was all excited about the fact that (under the hood) a named, enumerable value is actually stored as a number. There are ways, in both Visual Basic and C#, to use those numeric values.

I'm not going to show you how to do that because it's wrong, wrong, wrong. The point of using enumerated values is to get away from embedding magic numbers in your code and, instead, replace those values with meaningful names. Accessing the numeric value (a textbook example of an "implementation detail") violates the purpose of setting up an enumerated value in the first place.

More importantly, using those numeric values is just an accident looking for a place to happen because those numeric values are assigned positionally. If you're using those values in some "clever" way (sarcasm intended) then your code will break if someone inserts a new value into your Enum. At that point, every subsequent enumerated value gets assigned a new numeric value.

I do make one exception: If I want to be able to add two named values together to get a new value, then I use bit flags. But bit flags work by explicitly assigning every enumerated value a numeric value (no positional assignments) and then using the enumerated names without referring to the underlying numeric values. That's restrictive enough that I don't feel I'm violating my principles when I take advantage of it.

Posted by Peter Vogel on 04/23/2018 at 3:07 PM


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