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c#enumsattributesenum-flags

flag enum confusion C#

According to my code a=1, b=2, c=3 etc. I thought the flag would make a=1, b=2, c=4, etc

[Flags]
public enum someEnum { none, a, b, c, d, e, f, }

How do i get what i intended(c=4, e=8)? and what does the [Flags] mean above?

Solution

  • You can specify values for the enums, this is needed for flags cases:

    [Flags]
enum MyFlags {
  Alpha=1,
  Beta=2,
  Gamma=4,
  Delta=8
}

    what does the [Flags] mean above?

    It means the runtime will support bitwise operations on the values. It makes no difference to the values the compiler will generate. E.g. if you do this

    var x = MyFlags.Alpha | MyFlags.Beta;

    with the Flags attribute the result of x.ToString() is "Alpha, Beta". Without the attribute it would be 3. Also changes parsing behaviour.

    EDIT: Updated with better names, and the compiler doesn't complain using bitwise ops on a non-flags attribute, at least not C#3 or 4 (news to me).