How to make a countdown Timer continue even when Winform is closed?

Question

Hello. I'm new to windows form so I don't really understand how things work. Recently, I try to make a countdown timer that counts from a certain time to 0. But when the form is closed, everything is like "reset" and I don't want that. What I want is, for example, countdown time is 5 mins -> close form -> open form after 3 mins -> countdown time is 2 mins left. I wonder if you guys can share any ideas that will make it works and are simple so I can understand . Thanks in advance!

Answer 1

@Uyen Nguyen , Welcome to Microsoft Q&A, Based on your description, you want to make a countdown timer and hope that it will contine when the form is closed.

I make some steps and code example. You could check if it works for you.

First, I make a countdown Timer from the answer.

Second, I add the following settings in the winform.

Third, I used FormClosing event to save some information to the settings.

  private void Form1_FormClosing(object sender, FormClosingEventArgs e)  
        {  
            if(timer.IsRunnign)  
            {  
                Properties.Settings.Default.lefttime = label1.Text;  
                Properties.Settings.Default.Isrunning = true;  
                Properties.Settings.Default.closedtime=DateTime.Now;  
                Properties.Settings.Default.Save();  
            }  
        }  
  
 Fourth, I used Form1_Load event to read the information.  
  
  private void Form1_Load(object sender, EventArgs e)  
        {  
            if (Properties.Settings.Default.Isrunning== true)  
            {  
                string lefttime = Properties.Settings.Default.lefttime;  
                TimeSpan time1=TimeSpan.ParseExact(lefttime, @"mm\:ss", CultureInfo.CurrentCulture);  
                DateTime closedtime = Properties.Settings.Default.closedtime;  
                TimeSpan passedtime = DateTime.Now - closedtime;  
                var t = time1.Subtract(passedtime);  
                label1.Text=t.ToString(@"mm\:ss");  
                timer.SetTime(t.Minutes, t.Seconds);  
                timer.Start();  
                timer.TimeChanged += () => { label1.Text = timer.TimeLeftStr; };  
  
                // show messageBox on timer = 00:00.000  
                timer.CountDownFinished += () => { timer.Stop(); MessageBox.Show("Timer finished the work!"); };  
  
                //timer step. By default is 1 second  
                timer.StepMs = 1; // for nice milliseconds time switch  
            }  
            else  
            {  
                //set to 5 mins  
                timer.SetTime(5, 0);  
  
                //update label text  
                timer.TimeChanged += () => { label1.Text = timer.TimeLeftStr; };  
  
                // show messageBox on timer = 00:00.000  
                timer.CountDownFinished += () => { timer.Stop(); MessageBox.Show("Timer finished the work!"); };  
  
                //timer step. By default is 1 second  
                timer.StepMs = 1; // for nice milliseconds time switch  
            }  
             
        }  

Finally, Please set the properties when we click the stop button.

Completed code:

 public partial class Form1 : Form  
    {  
        public Form1()  
        {  
            InitializeComponent();  
        }  
        CountDownTimer timer = new CountDownTimer();  
        private void Form1_Load(object sender, EventArgs e)  
        {  
            if (Properties.Settings.Default.Isrunning== true)  
            {  
                string lefttime = Properties.Settings.Default.lefttime;  
                TimeSpan time1=TimeSpan.ParseExact(lefttime, @"mm\:ss", CultureInfo.CurrentCulture);  
                DateTime closedtime = Properties.Settings.Default.closedtime;  
                TimeSpan passedtime = DateTime.Now - closedtime;  
                var t = time1.Subtract(passedtime);  
                label1.Text=t.ToString(@"mm\:ss");  
                timer.SetTime(t.Minutes, t.Seconds);  
                timer.Start();  
                timer.TimeChanged += () => { label1.Text = timer.TimeLeftStr; };  
  
                // show messageBox on timer = 00:00.000  
                timer.CountDownFinished += () => { timer.Stop(); MessageBox.Show("Timer finished the work!"); };  
  
                //timer step. By default is 1 second  
                timer.StepMs = 1; // for nice milliseconds time switch  
            }  
            else  
            {  
                //set to 5 mins  
                timer.SetTime(5, 0);  
  
                //update label text  
                timer.TimeChanged += () => { label1.Text = timer.TimeLeftStr; };  
  
                // show messageBox on timer = 00:00.000  
                timer.CountDownFinished += () => { timer.Stop(); MessageBox.Show("Timer finished the work!"); };  
  
                //timer step. By default is 1 second  
                timer.StepMs = 1; // for nice milliseconds time switch  
                Console.WriteLine(Properties.Settings.Default.lefttime);  
            }  
             
        }  
  
        private void button1_Click(object sender, EventArgs e)  
        {  
            timer.Start();  
        }  
  
        private void button2_Click(object sender, EventArgs e)  
        {  
            timer.Pause();  
        }  
  
        private void button3_Click(object sender, EventArgs e)  
        {  
            timer.Stop();  
            timer.Dispose();  
            Properties.Settings.Default.lefttime = "";  
            Properties.Settings.Default.Isrunning = false;  
            Properties.Settings.Default.closedtime = DateTime.Now;  
            Properties.Settings.Default.Save();  
        }  
  
        private void Form1_FormClosing(object sender, FormClosingEventArgs e)  
        {  
            if(timer.IsRunnign)  
            {  
                Properties.Settings.Default.lefttime = label1.Text;  
                Properties.Settings.Default.Isrunning = true;  
                Properties.Settings.Default.closedtime=DateTime.Now;  
                Properties.Settings.Default.Save();  
            }  
        }  
    }  
    public class CountDownTimer : IDisposable  
    {  
        public Stopwatch _stpWatch = new Stopwatch();  
  
        public Action TimeChanged;  
        public Action CountDownFinished;  
  
        public bool IsRunnign => timer.Enabled;  
  
        public int StepMs  
        {  
            get => timer.Interval;  
            set => timer.Interval = value;  
        }  
  
        private Timer timer = new Timer();  
  
        private TimeSpan _max = TimeSpan.FromMilliseconds(30000);  
  
        public TimeSpan TimeLeft => (_max.TotalMilliseconds - _stpWatch.ElapsedMilliseconds) > 0 ? TimeSpan.FromMilliseconds(_max.TotalMilliseconds - _stpWatch.ElapsedMilliseconds) : TimeSpan.FromMilliseconds(0);  
  
        private bool _mustStop => (_max.TotalMilliseconds - _stpWatch.ElapsedMilliseconds) < 0;  
  
        public string TimeLeftStr => TimeLeft.ToString(@"mm\:ss");  
  
        public string TimeLeftMsStr => TimeLeft.ToString(@"mm\:ss\.fff");  
  
        private void TimerTick(object sender, EventArgs e)  
        {  
            TimeChanged?.Invoke();  
  
            if (_mustStop)  
            {  
                CountDownFinished?.Invoke();  
                _stpWatch.Stop();  
                timer.Enabled = false;  
            }  
        }  
  
        public CountDownTimer(int min, int sec)  
        {  
            SetTime(min, sec);  
            Init();  
        }  
  
        public CountDownTimer(TimeSpan ts)  
        {  
            SetTime(ts);  
            Init();  
        }  
  
        public CountDownTimer()  
        {  
            Init();  
        }  
  
        private void Init()  
        {  
            StepMs = 1000;  
            timer.Tick += new EventHandler(TimerTick);  
        }  
  
        public void SetTime(TimeSpan ts)  
        {  
            _max = ts;  
            TimeChanged?.Invoke();  
        }  
  
        public void SetTime(int min, int sec = 0) => SetTime(TimeSpan.FromSeconds(min * 60 + sec));  
  
        public void Start()  
        {  
            timer.Start();  
            _stpWatch.Start();  
        }  
  
        public void Pause()  
        {  
            timer.Stop();  
            _stpWatch.Stop();  
        }  
  
        public void Stop()  
        {  
            Reset();  
            Pause();  
        }  
  
        public void Reset()  
        {  
            _stpWatch.Reset();  
        }  
  
        public void Restart()  
        {  
            _stpWatch.Reset();  
            timer.Start();  
        }  
  
        public void Dispose() => timer.Dispose();  
    }  

Tested result:

Hope this could help you.

Best Regards,
Jack

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