Caculate how many one in a bit format of int value

Everyone knows that in computer, no matter what type you are using, finally it will be represent with bits , 0 and 1 .   For example
INT value    Bit
1                  0001
2                  0010
3                  0011
4                  0100
and so on....

A couple days ago, I was asked, given an int value, can you print out it in bit format, and caculate how many 1 in the bit level.

First of all, it is quite easy to get the bit string of the int value, just use convert function.
Secondly , caculate how many one in the bit string, you can use & operator and >> operator

   1:  class MainClass

   2:      {

   3:          static readonly int LENOFBIT = 8;

   4:          public static void Main (string[] args)

   5:          {

   6:              int iValueToTest = 12345;

   7:              string strBit = Convert.ToString(iValueToTest,2);

   8:              Console.WriteLine("int value {0} in bit format is {1}",iValueToTest,strBit);

   9:              Console.WriteLine("there are {0} one in bit format",CaculateOne(iValueToTest));

  10:                          

  11:          }

  12:          

  13:          static int CaculateOne(int iValue)

  14:          {

  15:              int iResult = 0;

  16:              int iLen = sizeof(int);

  17:              for(int i=0;i<iLen * LENOFBIT;i++)

  18:              {

  19:                  if((iValue & 1) == 1)

  20:                  {

  21:                      iResult ++;

  22:                  }

  23:                  iValue = iValue >> 1;

  24:              }

  25:              return iResult;

  26:          }

  27:          

  28:      }

You may ask , what the hell this is used for? assume you are implementing a user permission system,  you can use each bit to represent a permission, thus an int value can represent 32 permissions.