display timespan nicely

Excuse the rough code, I'm trying to display the duration of videos given the time in seconds. I've had a go below but it's not working properly.

I want it to just display nicely - i.e should display 9m:59s not 09m:59s.

If hours are zero dont display hours, if minutes are zero dont display minutes.

public static string GetTimeSpan(int secs)
{
    TimeSpan t = TimeSpan.FromSeconds(secs);

    string answer;
    if (secs < 60)
    {
        answer = string.Format("{0:D2}s", t.Seconds);
    }
    else if (secs < 600)//tenmins
    {
        answer = string.Format("{0:m}m:{1:D2}s", t.Minutes, t.Seconds);

    }
    else if (secs < 3600)//hour
    {
        answer = string.Format("{0:mm}m:{1:D2}s", t.Minutes, t.Seconds);
    }
    else
    {
        answer = string.Format("{0:h}h:{1:D2}m:{2:D2}s",
                                    t.Hours,
                                    t.Minutes,
                                    t.Seconds);
    }

    return answer;
}