如何只在一个标签中显示三个文本框的时间？

private void timer_click1(object sender, RoutedEventArgs e)
{
    seconds = seconds - 1;
    if (seconds == -1)
    {
        minutes = minutes - 1;
        seconds = 59;
    }
    if (minutes == -1)
    {
        hours = hours - 1;
        minutes = 59;
    }
    if (hours == 0 && minutes == 0 && seconds == 0)
    {
        timer.Stop();
    }
    string hhr = Convert.ToString(hours);
    string minns = Convert.ToString(minutes);
    string seccs = Convert.ToString(seconds);
}
private void timer_click1(object sender, Routed