Question

I have the following class:

class MyTimer
{
    class MyTimerInvalidType : SystemException
    {
    }
    class MyTimerNegativeCycles : SystemException
    {
    }

    private Timer timer = new Timer(1000);
    private int cycles = 0;

    public int Cycle
    {
        get
        {
            return this.cycles;
        }

        set
        {
            if(value >= 0)
                this.cycles = value;
            else
                throw new MyTimerNegativeCycles();
        }
    }

    private void timer_Tick(object sender, ElapsedEventArgs e)
    {
        try
        {
            this.Cycle--;
        }
        catch
        {
            this.Cycle = 0;
            timer.Stop();
        }
    }

    public MyTimer()
    {
        this.Cycle = 20;

        timer.Elapsed += new ElapsedEventHandler(timer_Tick);
        timer.Start();
    }
}

In my MainWindow class I have a List I add a MyTimer to when a button is pressed:

private List<MyTimer> timers = new List<MyTimer>();

private void testbtn_Click(object sender, RoutedEventArgs e)
{
    timers.Add(new MyTimer());
}

I tried to pass a label to the MyTimer class as a ref and update it but that won’t work (can’t access UI elements from another thread).

What is a good way to show the MyTimer.Cycle in a label so that it updates everytime the value is changed?

I must be able to “bind” each MyTimer to a different label from the code (or not bind it to a label at all).

Answer 1

You should use the BeginInvoke or Invoke method of the Dispatcher property of your label to change anything on your label or call any of it’s methods:

private void timer_Tick(object sender, ElapsedEventArgs e)
{
    try
    {
        this.Cycle--;
        this.label.Dispatcher.BeginInvoke(new Action(
            () => { label.Text = this.Cycle.ToString(); } ));
    }
    catch
    {
        this.Cycle = 0;
        timer.Stop();
    }
}

See Remarks section of the Dispatcher class or Dispatcher property.