Is an empty flag a bad habit?

Question

I faced a very stupid bug a few days ago. It was caused by this enum I get from third-party library:

[Flags]
public enum MyStatus
{
    OKResponse = 0,
    ResponseTooBig = 1,
    ErrorMessage = 2,
    NoResponse = 4,
    ...
}

I am used to check flags this way:

if ((status & MyStatus.OKResponse) != 0) {...}

but it doesn't work for MyStatus.OKResponse, because it is zero. It is not a flag at all, it is an absence of all flags. Of course, when I found the bug, I realised OKResponse was the only non error status, so it really means "no errors, no flags". However, I really don't find it obvious.

Is it a bad habit defining 0 as one of values in flags enum? What is the recommended way? What is the best way to check flags, that would work with "no flags" flag, too?

Is an empty flag a bad habit?

2 Answers