Calculating the number of bits in a Subnet Mask in C#

Question

I have a task to complete in C#. I have a Subnet Mask: 255.255.128.0.

I need to find the number of bits in the Subnet Mask, which would be, in this case, 17.

Answer 1

Bit counting algorithm taken from:
http://www.necessaryandsufficient.net/2009/04/optimising-bit-counting-using-iterative-data-driven-development/

string mask = "255.255.128.0";
int totalBits = 0;
foreach (string octet in mask.Split('.'))
{
    byte octetByte = byte.Parse(octet);
    while (octetByte != 0)
    {
        totalBits += octetByte & 1;     // logical AND on the LSB
        octetByte >>= 1;            // do a bitwise shift to the right to create a new LSB
    }                
}
Console.WriteLine(totalBits);

The most simple algorithm from the article was used. If performance is critical, you might want to read the article and use a more optimized solution from it.