int转时间
public static string FormatDuration(int duration)
{
if (duration == 0) return "00:00:00";
int hours = duration / 3600;
int minutes = duration % 3600 / 60;
int seconds = duration % 3600 % 60;
string _hours = hours.ToString("00") + ":";
string _minutes = minutes.ToString("00") + ":";
string _seconds = seconds.ToString("00");
return _hours + _minutes + _seconds;
}