WPF and Silverlight Timer


Users of Windows Forms will know that there are three timer objects you can use, namely the Windows Forms Timer, the System Timers Timer and finally the System Threading Timer, as the following example demonstrates;

Note: this tutorial is in both C# and Visual Basic, so look beneath the Visual Basic examples for the C# Version.

Visual Basic

Public Class Form1

 

    Dim timerCallBack As System.Threading.TimerCallback

 

    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load

        ”Winforms Timer

        Dim wfTimer As System.Windows.Forms.Timer()

 

        ”Timers Timer

        Dim tTimer As System.Timers.Timer()

 

        ”Threading Timer

        timerCallBack = AddressOf PrintTime

        Dim thTimer As System.Threading.Timer = New System.Threading.Timer(Me.timerCallBack)

 

 

    End Sub

 

    Private Sub PrintTime(ByVal obj As System.Object)

        ”Print the time to screen

    End Sub

 

 

End Class

C#

using System.Windows.Forms;

 

namespace TimersExample

{

    public partial class Form1 : Form

    {

        System.Threading.TimerCallback timerCallBack;

 

        public Form1()

        {           

            InitializeComponent();

        }

        private void Form1_Load(object sender, System.EventArgs e)

        {

            // Winforms Timer

            System.Windows.Forms.Timer wfTimer = new Timer();

 

            //Timers Timer

            System.Timers.Timer tTimer = new System.Timers.Timer();

 

            //Threading Timer

            timerCallBack = new System.Threading.TimerCallback(PrintTime);

            System.Threading.Timer thTimer = new System.Threading.Timer(this.timerCallBack);

        }

        private void PrintTime(object obj)

        {

            //Print the time to screen

        }

 

    }

}

 

In both WPF and Silverlight there is a new timer (the fourth .NET framework timer) called the System.Windows.Threading.DispatcherTimer. To demonstrate how this works, look at the following simple code sample. In it, there is some XAML that declares a label, button and a button click and window loaded events (In Silverlight use the UserControl_Loaded event for the page instead of Window_Loaded).

 

<Window x:Class="WpfTimer.Window1"

   xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation&quot;

   xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml&quot;

   Title="Window1" Height="300" Width="300" Loaded="Window_Loaded">

    <Grid>

 

        <StackPanel Orientation="Vertical">

        <Label Height="28" Width="70" Name="label1">Label</Label>

        <Button Height="23" Width="70" Name="button1" Click="button_Click">Button</Button>

 

        </StackPanel>

 

    </Grid>

</Window>

 

Note that in the Visual Basic XAML you have Window x:Class="Window1" at the top (in case you’re wondering why the XAML does not compile). In the code behind, you have the following code that instantiates a DispatcherTimer in the load event of the Window, and allows a user from starting and stopping the timer by toggling the button click event.

   

Visual Basic

Class Window1

    Dim timer As System.Windows.Threading.DispatcherTimer

    Public Event UpdateTime()

 

    Private Sub Window_Loaded(ByVal sender As Object, ByVal e As RoutedEventArgs)

        timer = New System.Windows.Threading.DispatcherTimer()

        timer.Interval = TimeSpan.FromSeconds(1)

        AddHandler timer.Tick, AddressOf timer_Tick

 

    End Sub

 

    Sub timer_Tick(ByVal sender As Object, ByVal e As EventArgs)

        Me.label1.Content = DateTime.Now.ToLongTimeString()

    End Sub

 

    Private Sub button1_Click(ByVal sender As Object, ByVal e As RoutedEventArgs)

        If Not Me.timer.IsEnabled Then

            Me.timer.Start()

            Me.button1.Content = "Stop"

        Else

            Me.timer.[Stop]()

            Me.button1.Content = "Start"

        End If

    End Sub

 

 

 

 

End Class

 

C#

using System;

using System.Windows;

 

namespace WpfTimer

{

    /// <summary>

    /// Interaction logic for Window1.xaml

    /// </summary>

    public partial class Window1 : Window

    {

        System.Windows.Threading.DispatcherTimer timer;

 

        public Window1()

        {

            InitializeComponent();         

        }

        private void Window_Loaded(object sender, RoutedEventArgs e)

        {

            timer = new System.Windows.Threading.DispatcherTimer();

            timer.Interval = TimeSpan.FromSeconds(1);

            timer.Tick += new EventHandler(timer_Tick);

        }

 

        void timer_Tick(object sender, EventArgs e)

        {

            this.label1.Content = DateTime.Now.ToLongTimeString();

        }

 

        private void button_Click(object sender, RoutedEventArgs e)

        {

            if (!this.timer.IsEnabled)

            {

                this.timer.Start();

                this.button1.Content = "Stop";

            }

            else

            {

                this.timer.Stop();

                this.button1.Content = "Start";

            }

        }

 

 

    }

}

 

DispatcherTimer

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