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

The count is equivalent to counting how many bits are set to 1 in the integer value of the enum.

There are very fast ways of doing this in C/C++, which you can adapt to C#:

e.g.

int bitcount(unsigned int n) {
   /* works for 32-bit numbers only    */
   /* fix last line for 64-bit numbers */

   register unsigned int tmp;

   tmp = n - ((n >> 1) & 033333333333)
           - ((n >> 2) & 011111111111);
   return ((tmp + (tmp >> 3)) & 030707070707) % 63;
}

Taken from here.

EDIT
Provided link is dead. Found another one that probably contains the same content.