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I stumbled upon a code where my colleague has recently modified an existing enum and added another enum just before the last enum, I am guessing he may have done this because the last enum was None(we are not in the same timezone to discuss).

My worry is if any code in the solution tries to fetch the integer value of None Enum(which I couldn't find anywhere luckily, but what about some code tries to do in future), then this will potentially produce wrong results.

Wouldn't it be safe to?

  1. Either Add Enum in the last
  2. Or associate an integer value against each enum so that ordering issue can be resolved?

Please throw some light.

Update: In one of the SO question, I read @Marc Gravell mentioning that inserting in the middle is dangerous, did I understand him correctly? Please see https://stackoverflow.com/a/12716043/2719527

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  • If you have never used some enum item in the whole code base, how can you break the code by pushing this item down by one (if this is last item)? Commented Apr 26, 2018 at 20:25
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    @T.S. the compiler autogenerates a backing value - if you cast it the value will be different if you add a new value between existing ones. Commented Apr 26, 2018 at 20:25
  • Yes, your two suggested options are safer in cases where you have code that expects certain enum values to have specific integer values associated with them, but that's kind of a bad practice also. In general, your colleague's change should be ok. Commented Apr 26, 2018 at 20:36
  • @DanielA.White I understand that. But if he said, it is not used then it can't be broken. There are many variables. Is code used as third-party code? etc Commented Apr 26, 2018 at 20:36
  • "None" should really always be the first item, since automatically filled in empty variable of that type (like, class variables or arrays elements) will be initialized to the first value (the one with integer value 0). That said, unless the enum has specific numbers defined in it, it should never, ever be used as or compared to an integer. Commented Apr 26, 2018 at 21:38

2 Answers 2

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There is no problem with adding new values at any place in enum list, because when the code with new enum in place is recompiled, the compiler figures out proper ordinals for all values.

There would be a problem if instances of the old enum were persisted, say, to a database. In this case assigning values explicitly would be a better alternative, because stored values would not be changed by a recompile, and would translate to incorrect values on retrieval.

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Some Enums in my project has a pretty long list, like 20 members what not, assigning a value wouldn't be little too much ?
@Vivek_Shukla unless you do something like if (someEnum == 1) or its stored in the DB. You will be fine without a number assigned
@Vivek_Shukla Both Marc's points are applicable to any enum modifications, in the middle or at the end. His second point, about serialization, is identical to what I said about persisting an enum value.
@dasblinkenlight My interpretation of his comment was that it can be really dangerous if there is code which is using its integer value, i.e. public enum Status { Good, Fair, Poor } (UInt16)Status.Good. Please throw some light on the DB part.
It's dangerous if you're storing enum values in a database, and then the enum changes in such a way that the values are now associated with different enum names. If you found that Something.Status == Poor and you saved that to the database as Something.Status = 2, then later you insert a new value before Poor in your enum definition, that historical record, when pulled from the database and presented in some UI, will look like Something.Status = NewInsertedStatus
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If you are concerned about breaking changes, do either thing that you suggest. The safest is always to assign a value to each member, that way it is explicit and you don't depend on the compiler generating something for you.

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Some Enums in my project has a pretty long list, like 20 members what not, assigning a value wouldn't be little too much ?
@Vivek_Shukla not if you do it the first time.
@Vivek_Shukla you technically only have to assign values to the last item and the inserted item if you're worried about too much typing. For example: public enum Status { Good, Fair, Poor, InsertedItem = 4, Bad = 3}
@RufusL I like your suggestion.
Just don't add another item after Bad without assigning it, or it will also be automatically assigned a value of 4..

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