c# 숫자앞에 0 넣기

int a_hour = (int)(_time / 3600);

int a_min = (int)_time % 3600 / 60;

int a_sec = (int)_time % 3600 % 60;

string.Format ("{0:D2} : {1:D2} : {2:D2}", a_hour, a_min, a_sec);

 

=> 01:59:06