Clearing Enum Flags

UPDATE: It looks like I am confusing a lot of people with this article. I wanted to write an article about something else than the title suggests (how flags enum are built) but I did not explain it well and what’s more important I forgot to mention the most important thing: how to simply clear a flag. I apologize for the confusion and here is the simple way of just clearing a flag:

[Flags]

public enum Foos {

    A = 1,

    B = 2,

    C = 4,

    D = 8,

    AB = A | B,

    CD = C | D,

    All = AB | CD

}

static class Program {

    static void Main() {

        Foos value = Foos.AB;

        Console.WriteLine(ClearFlag(value,Foos.A);

    }

    public static Foos ClearFlag(Foos value, Foos flag) {

       return value & ~flag;

    }

}

… I will try to write the other article some other time :-)

Comments

• Anonymous
  August 29, 2006
  Maybe there are side-effects, but the easiest C# version is:
  
  public static Foos ClearFlag( Foos value, Foos flag )
  {
   value &= ~flag;
   return value;
  }
  
• Anonymous
  August 29, 2006
  Clearing Enum Flags Via Krzysztof Cwalina - Somebodyjust pointed out to me that the enum guidelines don’t
• Anonymous
  August 29, 2006
  This is the first time I've seen someone xor the enum instead of and-not it, like Thomas shows.
  Why is this better?
• Anonymous
  February 12, 2007
  為什麼推薦 ? Krzysztof Cwalina 是 .NET Framework API Design Team 的 Program Manager, 他也寫了 一本 Framework Design