当Timer Control中的时间结束时，什么事件对行动负责？

Question

My program is some kind of test. The time of passing test is limited(20 minutes). When the time is out, the test must be finished and MessageBox appears with results of test. In Form_Load :

timer1.Tick += new EventHandler(timer1_Tick);
timer1.Interval = (1000) * (1);
timer1.Enabled = true;
timer1.Start();

private void timer1_Tick(object sender, EventArgs e)
        {            
            timer_label.Text = Convert.ToString(time);
            --time;
        }

How to finish test when time == 0 ? And why time in timer_label changes with step 2?(eg 1999, 1997, 1995...)

Answer 1

How to finish test when time == 0?

Timer just raises even on some interval. You should start timer for that. If you don't want events to be raised anymore, you should stop timer. You can do it directly in Tick event handler:

private void timer1_Tick(object sender, EventArgs e)
{            
    timer_label.Text = Convert.ToString(time);
    time--;

    if (time == 0)
       timer1.Stop();
}

Second question:

And why time in timer_label changes with step 2?(eg 1999, 1997, 1995...)

From your code there is no reason for such behavior. Looks like you have subscribed to two timers, or you have two event handlers of same timer Tick event. Also make sure you don't have decrement operator when displaying time, something like this:

timer_label.Text = Convert.ToString(--time);
--time;