Windows CountDown example

for making a simple countdown timer app create a project with the name ClockApp and have the following layout at mainpage.xaml


<phone:PhoneApplicationPage 
    x:Class="ClockApp.MainPage"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:phone="clr-namespace:Microsoft.Phone.Controls;assembly=Microsoft.Phone"
    xmlns:shell="clr-namespace:Microsoft.Phone.Shell;assembly=Microsoft.Phone"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    mc:Ignorable="d" d:DesignWidth="480" d:DesignHeight="768"
    FontFamily="{StaticResource PhoneFontFamilyNormal}"
    FontSize="{StaticResource PhoneFontSizeNormal}"
    Foreground="{StaticResource PhoneForegroundBrush}"
    SupportedOrientations="Portrait" Orientation="Portrait"
    shell:SystemTray.IsVisible="True">

    <!--LayoutRoot is the root grid where all page content is placed-->
    <Grid x:Name="ContentGrid" Grid.Row="1">
        <TextBlock x:Name="Countdown" VerticalAlignment="Center" FontFamily="quartzitalic.ttf#Quartz" Foreground="{StaticResource PhoneAccentBrush}" FontSize="64" HorizontalAlignment="Center" />
    </Grid>

    <!--Sample code showing usage of ApplicationBar-->
    <!--<phone:PhoneApplicationPage.ApplicationBar>
        <shell:ApplicationBar IsVisible="True" IsMenuEnabled="True">
            <shell:ApplicationBarIconButton IconUri="/Images/appbar_button1.png" Text="Button 1"/>
            <shell:ApplicationBarIconButton IconUri="/Images/appbar_button2.png" Text="Button 2"/>
            <shell:ApplicationBar.MenuItems>
                <shell:ApplicationBarMenuItem Text="MenuItem 1"/>
                <shell:ApplicationBarMenuItem Text="MenuItem 2"/>
            </shell:ApplicationBar.MenuItems>
        </shell:ApplicationBar>
    </phone:PhoneApplicationPage.ApplicationBar>-->

</phone:PhoneApplicationPage>

just have the code at mainpage.xaml.cs


using System;
using System.Collections.Generic;
using System.Linq;
using System.Net;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Animation;
using System.Windows.Shapes;
using Microsoft.Phone.Controls;
using System.Windows.Threading;

namespace ClockApp
{
    public partial class MainPage : PhoneApplicationPage
    {
        private DispatcherTimer timer;

        public MainPage()
        {
            InitializeComponent();

            Loaded += OnLoaded;
        }

        private void OnLoaded(object sender, RoutedEventArgs e)
        {
            timer = new DispatcherTimer
            {
                Interval = TimeSpan.FromSeconds(1)
            };

            timer.Tick += OnTick;

            timer.Start();
        }

        private void OnTick(object sender, EventArgs e)
        {
            var midnight = DateTime.Today.AddHours(24);
            var timeLeft = midnight - DateTime.Now;

            Countdown.Text = String.Format("{0:D2}:{1:D2}:{2:D2}", timeLeft.Hours, timeLeft.Minutes, timeLeft.Seconds);
        }
    }
}