Skip to main content

What is DispatcherTimer in wpf?

Image
By

DispatcherTimer

When you want to set a timer working with GUI, you always come across threading problem. The problem is that if you want to send some changes to UI that is constantly/continuously changing then that will make your UI unresponsive or in other words it will hang your UI.

 

To overcome from this situation, WPF gives us DispatcherTimer threading functionality that will take care of such continuously changing processing on UI thread and that will not hang your UI.

We can accomplish same scenario in Win Form, through System.Windows.Forms.Timer and in WPF it is System.Windows.Threading.DispatcherTimer.

 

Difference between DispatcherTimer and Regular timer (System.Timers.Timer)

DispatcherTimer is the regular timer. It fires its Tick event on the UI thread, you can do anything you want with the UI.

System.Timers.Timer is an asynchronous timer, its Elapsed event runs on a thread pool thread.

You have to be very careful in your event handler, you are not allowed to touch any UI component.

And you'll need to use the lock statement where ever you access class members that are also used on the UI thread.

 

Example

Here, I am posting an example how to use DispatcherTimer.

The example is to show counter that starts counting from 0. We have Start and Stop buttons to start counting and stop counting.

 

The UI would be look like this:

 

 

XAML code for UI:

<Window x:Class="DispatcherTimerExample.MainWindow"

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

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

        Title="MainWindow" Height="95" Width="525">

    <Grid Margin="10">

    <Grid.ColumnDefinitions>

      <ColumnDefinition Width="Auto" />

      <ColumnDefinition Width="*" />

      <ColumnDefinition Width="Auto" />

      <ColumnDefinition Width="Auto" />

    </Grid.ColumnDefinitions>   

    <TextBlock Grid.Column="0"

               Height="23"

               HorizontalAlignment="Left"

               Margin="5"

               Name="textBlock1"

               Text="Timer Value:"

               VerticalAlignment="Top" />

    <TextBox Grid.Column="1"

             x:Name="txtStatus"

             IsReadOnly="True"

             Background="AliceBlue"

             Foreground="Red"

             Height="23"

             HorizontalAlignment="Left"

             Margin="5,5,0,0"

             VerticalAlignment="Top"

             Width="233"

             Text="Press start to count."/>

    <Button Content="Start"

            Grid.Column="2"

            Height="23"

            HorizontalAlignment="Left"

            Margin="5"

            Name="btnStart"

            VerticalAlignment="Top"

            Width="75"

            Click="btnStart_Click" />

    <Button Content="Stop"

            Grid.Column="3"

            Height="23"

            HorizontalAlignment="Left"

            Margin="5"

            Name="btnStop"

            VerticalAlignment="Top"

            Width="75"

            Click="btnStop_Click" />

  </Grid>

</Window>

 

Code behind for this application which contains use of DispatcherTimer.

 

Code C#:

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

using System.Windows;

using System.Windows.Controls;

using System.Windows.Data;

using System.Windows.Documents;

using System.Windows.Input;

using System.Windows.Media;

using System.Windows.Media.Imaging;

using System.Windows.Navigation;

using System.Windows.Shapes;

using System.Windows.Threading;

 

namespace DispatcherTimerExample

{

  /// <summary>

  /// Interaction logic for MainWindow.xaml

  /// </summary>

  public partial class MainWindow : Window

  {

   

    DispatcherTimer _timer;

    int count = 0;

 

    public MainWindow()

    {

      InitializeComponent();

      //Create new instance of DispaterTimer

      _timer = new DispatcherTimer();

 

      //The continuously changing properties should go under the Tick event handler

      //so that it could be taken into UI thread and UI stays responsive.

      _timer.Tick += new EventHandler(_timer_Tick);

    }

   

    void _timer_Tick(object sender, EventArgs e)

    {

      //Assigns count to the textblock.

      txtStatus.Text = (count++).ToString();

    }

 

    /// <summary>

    /// Starts the counting.

    /// </summary>

    /// <param name="sender"></param>

    /// <param name="e"></param>

    private void btnStart_Click(object sender, RoutedEventArgs e)

    {

      // Set the Interval

      _timer.Interval = TimeSpan.FromMilliseconds(Convert.ToDouble(1));

      // Start the timer

      _timer.Start();

      txtStatus.Text = "Started";

    }

 

    /// <summary>

    /// Stops the counting.

    /// </summary>

    /// <param name="sender"></param>

    /// <param name="e"></param>

    private void btnStop_Click(object sender, RoutedEventArgs e)

    {

      // Stop the timer

      _timer.Stop();

      txtStatus.Text = "Stopped at : " + count.ToString();

    }

  }

}

 

Use of DispatcherTimer

Other use of DispatcherTimer is ProgressBar functionality where you can show progress on certain property changes. I will try to post ProgressBar functionality of Start and End date.

 

DISCLAIMER ========== This e-mail may contain privileged and confidential information which is the property of Persistent Systems Ltd. It is intended only for the use of the individual or entity to which it is addressed. If you are not the intended recipient, you are not authorized to read, retain, copy, print, distribute or use this message. If you have received this communication in error, please notify the sender and delete all copies of this message. Persistent Systems Ltd. does not accept any liability for virus infected mails.

Labels:

Comments

Post a Comment

Popular posts from this blog

WPF-MVVM: RelayCommand Implementation

By
In WPF if we are implementing MVVM pattern then we need to play with Command rather than Events. You can use ICommand interface to create each command class. Implementation of ICommand in a class gives you CanExecute(), Execute() methods which take part in the action performed by Command.   Rather than making Command Class for each Command we can implement a generic Relay Command to get Command. Below is a RelayCommand class that we will implement.   ///   <summary>      ///  To register commands in MMVM pattern      ///   </summary>      class   RelayCommands  :  ICommand     {          readonly   Action < object > _execute;          readonly   Predicate < object > _canExecute;  ...
Post a Comment
Read more

iOS Dev: Encryption in Objective-C

By
Hello Friends: In this Article/Post, I introduced the one encryption technique in Objective-C.  Encryption Component Features in all  Symmetric Encryption: AES, Blowfish, Twofish, RC2, ARC4, DES, 3DES, PBES1, PBES2. Hash Algorithms :  SHA-1 , SHA256, SHA384, SHA512, MD2, MD4, MD5, HAVAL. Hash Algorithms: RIPEMD128, RIPEMD160, RIPEMD256, RIPEMD320. Encoding: Base64, hex, quoted-printable,  URL-encoding . HMAC with any supported hash algorithm: HMAC-MD5,  HMAC-SHA1 , etc. Password-based Key Derivation Functions: PBKDF1, PBKDF2 PKCS7 -- P7S and P7M creation, decryption, verification. Public key encryption/decryption with digital certificates. Digital signature creation/verification with digital certificates. Bzip2 in-memory compression. Encrypt / decrypt strings or byte data. Return encrypted data as Base64, quoted-printable, or hex-encoded strings. Hash strings or binary data using SHA1, MD2, MD5, HAVAL, SHA384, or SHA512. Public-key encryp...
1 comment
Read more

Reactive Extensions (Rx)

By
Reactive Extensions (Rx) What is Rx Rx is a library for composing asynchronous and event-based programs using observable collections. Using Rx, developers represent asynchronous data streams with Observables, query asynchronous data streams using LINQ operators, and parameterize the concurrency in the asynchronous data streams using Schedulers. Simply put, Rx = Observables + LINQ + Schedulers. The Reactive Extensions (Rx) is a library for composing asynchronous and event-based programs using observable sequences and LINQ-style query operators. Whether you are authoring a traditional desktop or web-based application, you have to deal with asynchronous and event-based programming from time to time. Desktop applications have I/O operations and computationally expensive tasks that might take a long time to complete and potentially block other active threads. Furthermore, handling exceptions, cancellation, and synchronization is difficult and error-prone. Thr...
Post a Comment
Read more