C# - Win Form stopping Timer tick

Question

This is my implementation of a Win Form app that has a countdown timer:

readonly DateTime myThreshold;
public Form1()
{
    InitializeComponent();

    myThreshold = Utils.GetDate();
    Timer timer = new Timer();
    timer.Interval = 1000; //1 second
    timer.Tick += new EventHandler(t_Tick);
    timer.Start();

    //Threshold check - this only fires once insted of each second
    if (DateTime.Now.CompareTo(myThreshold) > 0)
    {
        // STOP THE TIMER
        timer.Stop();
    }
    else
    {
        //do other stuff
    }
}

void t_Tick(object sender, EventArgs e)
{
    TimeSpan timeSpan = myThreshold.Subtract(DateTime.Now);
    this.labelTimer.Text = timeSpan.ToString("d' Countdown - 'hh':'mm':'ss''");
}

The wanted behavior is to stop the timer and the tick function when the threshold is reached.

This now does not happens because the check is only executed once since it is placed in the Form1 initialization.

Does exist a way to add this check in a way to immediately stop the Timer once a condition has been meet?

Answer 1

If we define timer as a class field (so it can be accessed from all methods in the class), then we can just add the check to the Tick event itself, and stop the timer from there:

private Timer timer = new Timer();

void t_Tick(object sender, EventArgs e)
{
    // Stop the timer if we've reached the threshold
    if (DateTime.Now > myThreshold) timer.Stop();

    TimeSpan timeSpan = myThreshold.Subtract(DateTime.Now);
    this.labelTimer.Text = timeSpan.ToString("d' Countdown - 'hh':'mm':'ss''");
}