c# how to make a synchronized timer with a web service

Question

I am making a multiplayer game in c# windows form application with web service which is requires us to put a timer on the gameform, so that when the countdown timer becomes 0, it would be the opponent's turn. Now, this is my timer code.

private void StartTimer()
{
   timeLeft = 11;
   while (TimerRunning)
   {
    if (timeLeft > 0)
     {
       if (this.InvokeRequired)
           lb_Timer.Invoke((MethodInvoker)delegate ()
           {
               timeLeft = timeLeft - 1;
               if (timeLeft < 10)
                   lb_Timer.Text = "0: 0" + timeLeft;
               else
                   lb_Timer.Text = "0: " + timeLeft;
           });
       else
       {
           timeLeft = timeLeft - 1;
           if (timeLeft < 10)
               lb_Timer.Text = "0: 0" + timeLeft;
           else
               lb_Timer.Text = "0: " + timeLeft;
       }
     }
     else
     {
       if (this.InvokeRequired)
           lb_Timer.Invoke((MethodInvoker)delegate ()
           {
               TimerRunning = false;
               lb_Timer.Text = "0:00";
           });
       else
       {
           TimerRunning = false;
           lb_Timer.Text = "0:00";

       }
       break;
    }
      Thread.Sleep(2200);
   }
}

Notes:

the countdown timer span is 10 seconds, I gave the timeleft value 11 so that when the timer starts, it would start at exactly 10s.
The thread.sleep becomes the interval for my timer, because 1000 or 1s is too fast, that's why I decided to make it to 2.2s.
can you give me an advice on how to make the thread stop, when the user attacks, so that the timer would reset?
can you give me any idea or tips on how should I implement my timer using the webservice? thank you!

I guess the given 'StartTimer()' method is a worker thread callback method, am I right? But, if you put the thread to sleep for 2200ms multiplied by 10, this is 22s, not 10s. You should also put your copy-and-pasted code (for invocation) into methods, that can be invoked, that is not so error-prone. Have a look at the 'Task' class and 'CancellationToken' struct in the 'System.Threading.Tasks' namespace. — KBO, Nov 21 '17 at 14:02
Thanks for the suggestion KBO! will look at those later, and also what do you mean by the copy-pasted code? The one that I used to call the method start timer? — Garry Stephenson, Nov 21 '17 at 23:47

score 0 · Answer 1 · answered Nov 23 '17 at 08:17

Here is a simple example how a countdown can be implemented. Create a new WinForms project and add two buttons and two labels. A click on btn_Start starts the countdown, a click on btn_Cancel cancels it. So you can play around a little bit. In your game, after the countdown task has finished with the boolean result, you can fire an event, set a shared boolean variable, set an AutoResetEvent or ...

public partial class Form1 : Form
{
  CancellationTokenSource _cancelSource = null;

  public Form1()
  {
    InitializeComponent();
  }

  private async void btn_Start_Click(object sender, EventArgs e)
  {
    btn_Start.Enabled = false;
    lb_Result.Text    = "Countdown started...";

    if(_cancelSource == null)
      _cancelSource = new CancellationTokenSource();
    else if (_cancelSource.IsCancellationRequested)
    { 
      _cancelSource.Dispose();
      _cancelSource = new CancellationTokenSource();
    }

    bool countDownCancelled = await PerformCountdown(_cancelSource.Token);

    if(countDownCancelled)
      lb_Result.Text = "Countdown cancelled";
    else
      lb_Result.Text = "Countdown finished";

    btn_Start.Enabled = true;
  }

  private void btn_Cancel_Click(object sender, EventArgs e)
  {
    if (_cancelSource != null && !_cancelSource.IsCancellationRequested)
      _cancelSource.Cancel();
  }

  private void UpdateTimeLabel(int remainingSeconds)
  {
    lb_Timer.Text = string.Format("0: {0}s", remainingSeconds);
  }

  private async Task<bool> PerformCountdown(CancellationToken cancelToken)
  {
    bool cancelled = false;

    try
    {
      int timeLeft = 3;

      Invoke((MethodInvoker)delegate() { UpdateTimeLabel(timeLeft); });
      do
      {
        await Task.Delay(1000, cancelToken);

        if (cancelToken.IsCancellationRequested)
          break;

        timeLeft--;
        Invoke((MethodInvoker)delegate() { UpdateTimeLabel(timeLeft); });
      }
      while (timeLeft > 0);
    }
    catch (OperationCanceledException)
    {
      cancelled = true;
      Debug.WriteLine("PerformCountdown cancelled");
    }
    catch (Exception ex)
    {
      Debug.WriteLine("PerformCountdown unhandled exception: " + ex);
    }

    return cancelled;
  }
}

c# how to make a synchronized timer with a web service

1 Answers1