Get number of flags from an enum variable

Code:

public static class EnumHelper 
{
    public static UInt32 NumFlags(this Enum e)
    {
        UInt32 v = Convert.ToUInt32(e);
        v = v - ((v >> 1) & 0x55555555);
        v = (v & 0x33333333) + ((v >> 2) & 0x33333333);
        UInt32 count = ((v + (v >> 4) & 0xF0F0F0F) * 0x1010101) >> 24;
        return count;
    }
}

This is some kind of black magic, works very fast. Got here.