How to stop DispatcherTimer in c# WPF

Question

I am checking the time and when is equal to something I want to stop the dispatcher.

But it doesn't work. Timer is still working after calling Stop().

private void startTime(bool what)
{
    vartimer = new DispatcherTimer();

    if (!what)
    {
        MessageBox.Show("Start");

        timer.Interval = new TimeSpan(0, 0, 1);
        timer.Tick += setTime;
        timer.Start();
    }

    if (what)
    {
        MessageBox.Show("Stop");
        timer.Stop();
    }
}

When it starts, it is showing the Start text. When it should stop, it should show the Stop text but it is still working.

Did I do something wrong?

timer.stop();

Should stop the Dispatcher, right?

How many events do you get if stop was called? may be try to first stop then show the message box so it is already stopped when the box shows up. — Daniel W., Aug 21 '18 at 13:10
FYI, Dispatcher and DispatcherTimer are different classes, and they are not interchangeable — ASh, Aug 21 '18 at 13:36

mm8 · Accepted Answer · 2020-08-28T13:16:26.487

7

Define the DispacherTimer outside your method:

DispatcherTimer timer = new DispatcherTimer();
private void startTime(bool what)
{
    if (what == false)
    {
        MessageBox.Show("Start");

        timer.Interval = new TimeSpan(0, 0, 1);
        timer.Tick -= setTime;
        timer.Tick += setTime;
        timer.Start();
    }

    if (what == true)
    {
        MessageBox.Show("Stop");
        timer.Stop();
    }
}

In your current code, you are creating a new instance of the DispacherTimer each time the method is called.

edited Aug 28 '20 at 13:16

answered Aug 21 '18 at 13:25

mm8

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Thanks... And again i have to learn a lot ;) You have right. I always create new instance when i call the method like you said. Thanks a lot! – fullje Aug 21 '18 at 13:31

score 3 · Answer 2 · answered Aug 21 '18 at 13:16

Your instance of DispatcherTimer should be a private field of your class because everytime you are calling startTime(...), you are creating a new instance of the DispatcherTimer class that is started but never stopped. Here is an example of what could be done:

public class YourClass : IDisposable
{
    private readonly DispatcherTimer m_timer;

    public YourClass()
    {
          m_timer = new DispatcherTimer();
          m_timer.Interval = new TimeSpan(0, 0, 1);
          m_timer.Tick += setTime;            
    }

    public void Dispose()
    {
          m_timer.Tick -= setTime;    
          m_timer.Stop(); 
    }

    private void startTime(bool what)
    {
        if(what == false)
        {
            MessageBox.Show("Start");

            m_timer.Start();
        }

        if(what == true)
        {
            MessageBox.Show("Stop");

            m_timer.Stop();
        }
    }
}

I also added the IDisposable implementation to make sure the Dispatcher instance is properly unsubscribed from and stopped.

score 0 · Answer 3 · answered Aug 22 '18 at 03:50

Class A
{
  private DispatcherTimer _timer; // This is a global variable
  public void StartTime(bool what)
  {
   DispatcherTimer timer = new Dispatcher(); //This is a local variable
   ...
  }
}

When you call the StartTime function，the timer is a new instance. If you run StartTime(false) and StartTime(true), it will have two DispatcherTimer;

How to stop DispatcherTimer in c# WPF

3 Answers3