How to make a Countdown Timer in C#

In this article, we’ll walk through the creation of a countdown timer using a Windows Forms Application in C#. The application will include a graphical user interface (GUI) that displays the timer and buttons to start and stop it.

How to make a Countdown Timer in C#?

Open Visual Studio, then click New Project, then select Visual C# on the left, then Windows and then select Windows Forms Application. Name your project "Countdown" and then click OK

Design your form as shown below.

Add code to handle your form as below

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace Countdown
{
    public partial class Form1 : Form
    {
        System.Timers.Timer t;
        int h, m, s;

        public Form1()
        {
            InitializeComponent();
        }

        // Initialize the timer when the form loads
        private void Form1_Load(object sender, EventArgs e)
        {
            t = new System.Timers.Timer();
            t.Interval = 1000; // 1 second
            // Attach the event handler
            t.Elapsed += OnTimeEvent;
        }

        // Timer Elapsed Event
        private void OnTimeEvent(object sender, System.Timers.ElapsedEventArgs e)
        {
            // Use Invoke to update UI from a non-UI thread
            Invoke(new Action(() =>
            {
                s += 1;
                if (s == 60)
                {
                    s = 0;
                    m += 1;
                }
                if (m == 60)
                {
                    m = 0;
                    h += 1;
                }
                // Display time in hh:mm:ss format
                txtResult.Text = string.Format("{0}:{1}:{2}", h.ToString().PadLeft(2, '0'), m.ToString().PadLeft(2, '0'), s.ToString().PadLeft(2, '0'));
            }));
        }

        // Start the timer
        private void btnStart_Click(object sender, EventArgs e)
        {
            t.Start();
        }

        // Stop the timer
        private void btnStop_Click(object sender, EventArgs e)
        {
            t.Stop();
        }

        // Stop the timer when the form is closing
        private void Form1_FormClosing(object sender, FormClosingEventArgs e)
        {
            //Stop timer
            t.Stop();
            Application.DoEvents();
        }
    }
}

Since the timer runs on a separate thread, updating the UI requires marshaling the call to the UI thread. The Invoke method ensures that the UI is updated safely.

The timer is stopped in the FormClosing event to prevent it from continuing in the background after the form is closed.

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