C#:在按位枚举中获得最低值的键

Question

我有这样的枚举

[Flags]
public enum Key
{
  None = 0,
  A = 1,
  B = 2,
  C = 4
}

我有以下内容

Key k1 = Key.A | Key.B | Key.C;

我想得到k1中具有最低值的键.我怎样才能做到这一点？

例:

Key k1 = Key.A | Key.B | Key.C; // I want a 
Key k2 = Key.B | Key.C; // I want b
Key k3 = Key.A | Key.C; // I want a

Answer 1

你可以用一点技巧:

Key key = Key.B | Key.C;
Key lowest = (Key)((int)key & -(int)key);

Answer 2

Keys key = Keys.b | Keys.c;

var lowest = Enum.GetValues(typeof(Keys))
    .Cast<Keys>()
    .OrderBy(x => x)
    .FirstOrDefault(x => key.HasFlag(x));

LINQ方法的效率和.NET 4.0版本略高一些.