In C# please

(page 57 from out "Cracking the coding interview[...]" textbook):

The following code sums the digits in a number. What is its big 0 time? int sumDigits(int n) { int sum = 0; while (n > 0) { sum += n % 10; n /= 10; } return sum; }

Hint: in here you should give an answer for the big-Oh in terms of n.

Please place meaningful code comments for each line! I will be sure to upvote