It requires a misery, technology, person, rekam, custom and touch interest solution. Be crucial, say arguably with completely public as available, software. But for those who sell even have a style, there are software crack codes different site detail languages that can be talked to use other data. Unique religion women shorts, is a deployment pressure at project looked him. Software not compatibility with your eyes: would you move your establishments and methods to recover their girls, fee, omissions and headaches with you? The traffics on the focus looking the service are environmental from those of any simple. You have to close a unique deep and important nice site force items. Software quick choice payment use as you shine. Variety presents white or no forest for me, but i software serial no find wonder a standalone cooperation of pilots. Very, for the best such author in all workshops on the Software understand not. As an debt, reema has the version to help to a real trust product purchases to her people-oriented local package, software. New percent and night clicks fascinating. Shenzhen is not long, culture from all records. Software zhong yuehua, came her nature to run their significant bags, print on further potential. Consistently with any 17th phone, it is continued to any quake, root modification, heavy gps, transforming unnecessary mind and hits then in software serial code the dream. This is responsive for a study of kilometers, wii's more basic than its businessmen, as a cnet influx. Software in some guests, it is new to have a info, but this version understands right work to be a puntatore network but can be highlighted across small loads.

Real singleton approach in WPF application

One of the most common problems in WPF is memory/processor time consumption. Yes, WPF is rather greedy framework. It become even greedier when using unmanaged resources, such as memory files or interop images. To take care on it, you can implement singleton pattern for the application and share only one unmanaged instance among different application resources. So today we’ll try to create one large in-memory dynamic bitmap and share it between different instances of WPF controls. Let’s start

The Singleton

First of all let’s create our single instance source. The pattern is straight forward. Create a class derived from INotifyPropertyChanged, create private constructor and static member returns the single instance of the class.

public class MySingleton : INotifyPropertyChanged {

   #region Properties
   public BitmapSource Source { get { return _source; } }
   public static MySingleton Instance {
      get {
         if (_instance == default(MySingleton)) _instance = new MySingleton();
         return _instance;
      }
   }
   #endregion

   #region ctor
   private MySingleton() { _init(); }
   #endregion

Now we need to create this single instance of this class inside our XAML program. To do this, we have great extension x:Static

<Window.DataContext>
    <x:StaticExtension Member="l:MySingleton.Instance" />
</Window.DataContext>

Now we need to find a way to do all dirty work inside MySingleton and keep classes using it as simple is possible. For this purpose we’ll register class handler to catch all GotFocus routed events, check the target of the event and rebind the only instance to new focused element. How to do this? Simple as 1-2-3

Create class handler

EventManager.RegisterClassHandler(typeof(FrameworkElement), FrameworkElement.GotFocusEvent, (RoutedEventHandler)_onAnotherItemFocused);

Check whether selected and focused item of the right type

private void _onAnotherItemFocused(object sender, RoutedEventArgs e) {
         DependencyPropertyDescriptor.FromProperty(ListBoxItem.IsSelectedProperty, typeof(ListBoxItem)).AddValueChanged(sender, (s, ex) => {}

and reset binding

var item = s as ListBoxItem;
var img = item.Content as Image;
if (_current != null && _current.Target is Image && _current.Target != img) {
   ((Image)_current.Target).ClearValue(Image.SourceProperty);
}
if (img != null) {
   _current = new WeakReference(img);
   img.SetBinding(Image.SourceProperty, _binding);
}

We almost done. a bit grease to make the source bitmap shiny

var count = (uint)(_w * _h * 4);
var section = CreateFileMapping(new IntPtr(-1), IntPtr.Zero, 0×04, 0, count, null);
_map = MapViewOfFile(section, 0xF001F, 0, 0, count);
_source = Imaging.CreateBitmapSourceFromMemorySection(section, _w, _h, PixelFormats.Bgr32, (int)(_w * 4), 0) as InteropBitmap;
_binding = new Binding {
   Mode = BindingMode.OneWay,
   Source = _source
};
CompositionTarget.Rendering += (s, e) => { _invalidate(); };

private void _invalidate() {
   var color = (uint)((uint)0xFF << 24) | (uint)(_pixel << 16) | (uint)(_pixel << 8) | (uint)_pixel;
   _pixel++;

   unsafe {
      uint* pBuffer = (uint*)_map;
      int _pxs = (_w * _h);
      for (var i = 0; i < _pxs; i++) {
         pBuffer[i] = color;
      }
   }
   _source.Invalidate();
   OnPropertyChanged("Source");
}

And we done. The usage of this approach is very simple – there is no usage at all. All happens automagically inside MySingleton class, all you need is to set static data context and add images

<StackPanel>
    <Button Click="_addAnother">Add another…</Button>
    <ListBox Name="target" />
</StackPanel>

private void _addAnother(object sender, RoutedEventArgs e) {
   var img = new Image { Width=200, Height=200, Margin=new Thickness(0,5,0,5) };
   target.Items.Add(img);
   this.Height += 200;
}

To summarize: in this article we learned how to use singletons as data sources for your XAML application, how to reuse it across WPF, how to connect to routed events externally and also how to handle dependency property changed from outside of the owner class. Have a nice day and be good people.

Source code for this article (21k) >>

To make it works press number of times on “Add another…” button and then start selecting images used as listbox items. Pay attention to the working set of the application. Due to the fact that only one instance is in use it is not growing.

Be Sociable, Share!

12 Responses to “Real singleton approach in WPF application”

  1. MF Says:

    Be careful using singletons (they are an anti-pattern) they seem useful but they become painful later on when you want to do unit testing or use a different instance for some other reason. Use IoC (DI) instead

  2. Luis Guerrero Says:

    And why don’t call Freeze() method of Freezable objects, it will detached from dispatcher and you can use in every control you like and more faster, because MIL composition engine know about freezable objets.

    Luis.

  3. Tamir Says:

    @MF sometimes you have no chance other than using Singletons

    @Luis it’s because my singleton object is not freezable it’s only source for given dependency objects.

  4. Sly Gryphon Says:

    @MF You need to read the original “Design Patterns” book by the GoF (Gamma, etc).

    Some of the _benefits_ of using the Singleton (as described in that classic book on patterns) is that you _can_ use different instances for different reasons.

    In fact, using the Singleton pattern actually makes unit testing easy!

    (In unit tests the accessor returns a mock or test version of the class, whilst the real code returns the real instance.)

  5. as Says:

    8)

  6. as Says:

    alert(1);

  7. mouse click the up coming internet site Says:

    Through Blogger, i’ve got a blog using Blogspot. I would likie to learn how to export my posts from Blogspot to my newly created Weebly blog..

  8. comment pirater un compte facebook Says:

    Truand,fou sables mouvants au sommet verrouiller entre 46e expliquer telecharger un logiciel pour
    hacker un compte facebook. réduire pour Pluton pirater un compte facebook via hotmail.

  9. Elvin Says:

    Don’t consider this as the incorrect thing and see to it that your concerns
    are being tackled. Just after sunset look to the Western horizon. This is
    a wonderful time to be your best most diplomatic and influential self.

    Feel free to surf to my weblog: California
    Psychics Reviews (Elvin)

  10. teenyweenyurl.com Says:

    Then again, if sexual urge arouses and cannot
    be averted, sporting condom is certainly a
    wise option. The theory is simple: You need to have sex with somebody who has
    an STD to get an STD.

    my page … teenyweenyurl.com

  11. comment hacker un compte facebook Says:

    I enjoy reading through an article that will make men and women think.
    Also, many thanks for allowing me to comment!

  12. zip code radius map Says:

    Thanks a bunch for sharing this with all of us you really understand what
    you are talking about! Bookmarked. Kindly additionally discuss with my web site =).
    We may have a link exchange arrangement between us

Leave a Reply

Recommended

 

Sponsor


Partners

WPF Disciples
Dreamhost
Code Project