public partial class Form1 : Form
{

Timer myTimer = new Timer();
int timeLeft = 10;

    public Form1()
    {
        InitializeComponent();

        //set properties for the Timer
        myTimer.Interval = 1000;
        myTimer.Enabled = true;

        //Set the event handler for the timer, named "myTimer_Tick"
        myTimer.Tick += myTimer_Tick;

        //Start the timer as soon as the form is loaded
        myTimer.Start();

        //Show the time set in the "timeLeft" variable
        lblCountDown.Text = timeLeft.ToString();

    }

    private void myTimer_Tick(object sender, EventArgs e)
    {
        //perform these actions at the interval set in the properties.
        lblCountDown.Text = timeLeft.ToString();
        timeLeft -= 1;

        if (timeLeft < 0)
        {
            myTimer.Stop();
        }
    }
}

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