C# Enums: Nullable or 'Unknown' Value?

Question

If I have a class with an enum member and I want to be able to represent situations where this member is not defined, which is it better?

a) Declare the

Answer 1

You just have to decide whether you need a value to represent unknown values, or you do need a way to represent absence of any value.

In the case of a need to represent unknown values, an extra enum-member sounds good as a solution.

In case of a need to represent absence of any value, make it nullable.

Have in mind, that there is nothing wrong with having both "unknown" enum-member and the enum itself being nullable at the same time.

HTH.