Counting the number of flags set on an enumeration

Question

I\'m sure there must be a much better way of doing this. I\'m trying to do a count operation on a Flags enum. Before I was itterating over all the possible values and counting t

Answer 1

After looking on the site Assaf suggested I managed to find a slightly different solution that I got working for Int32's.

Here's the code for anyone else:

    internal static UInt32 Count(this Skills skills)
    {
        UInt32 v = (UInt32)skills;
        v = v - ((v >> 1) & 0x55555555); // reuse input as temporary
        v = (v & 0x33333333) + ((v >> 2) & 0x33333333); // temp
        UInt32 c = ((v + (v >> 4) & 0xF0F0F0F) * 0x1010101) >> 24; // count
        return c;
    }

Answer 2

int count = Enum.GetValues(typeof(Skills)).Length;

Answer 3

<FlagsAttribute()> _
Public Enum Skills As Byte
    None = 0
    Skill1 = 1
    Skill2 = 2
    Skill3 = 4
    Skill4 = 8
    Skill5 = 16
    Skill6 = 32
    Skill7 = 64
    Skill8 = 128
End Enum


    Dim x As Byte = Skills.Skill4 Or Skills.Skill8 Or Skills.Skill6
    Dim count As Integer
    If x = Skills.None Then count = 0 Else _
        count = CType(x, Skills).ToString().Split(New Char() {","c}, StringSplitOptions.RemoveEmptyEntries).Count

depends on the definition of "better".

the check for Skills.None is required because if no bits are on, the string() returns Skills.None which results in a count of 1. this would work the same for integer, long, and their unsigned relatives.