[WPF][5][3]Application object

[5][3]Application object

• It is an interface between your application and the system
• It is accessible from within all WPF .NET projects and provides an interface between your application and the system
• It is the entry point of a WPF application
• Threads in a WPF application must run in a singlethreaded apartment (STA)
• Main must be marked with an STAThread attribute.
• In the WPF sense, an application is a singleton object that provides services for UI components and UI programmers in the creation and execution of a WPF program.
• It works the same for both WPF XBAP and WPF Window Applications
• Application defines a Run method that keeps the application alive and dispatches messages appropriately
• 
  
  [STAThread]
  public static void Main()
  {

  Application app = new Application();
  MainWindow window = new MainWindow();
  window.Show();
  app.Run(window);

  }
  
  
• Application also defines a StartupUri property that provides an alternate means of showing the application’s first Window.
  
  
  [STAThread]
  public static void Main()
  {

  Application app = new Application();
  Application.Current.StartupUri = new Uri("MainWindow.xaml", UriKind.Relative);
  Application.Current.Run();

  }
  
  
• It offers the possibility to hook into events and override virtual methods for your application
• It acts similar to how the global.asax file manages contextual session and application information for ASP.NET applications
• Activated event /OnActivated virtual method: A window activated by the system
• Deactivated/Deactivated : A window deactivated by the system
• SessionEnding/OnSessionEnding: Raised when a user session ends or the operating, system terminates (i.e., logoff or shutdown)
• ReasonSessionEnding enumeration
  
• Exit/OnExit: Raised after all windows are destroyed
• Startup/OnStartup: Occurs prior to any windows being created or navigations being performed
• The Application object is defined by the MyApp.xaml file and its corresponding code-behind file.
• System.Windows.Application.Current
• the instance of application
• it is available once it is created

• The use of the Application object to share variables across pages is fundamental to its purpose
• Application.Current.Properties["MyName"] = "George Lache";
• Application defines a readonly Windows collection to give you access to all open Windows.
• MainWindow property
• A WPF application’s main window is the top-level window that is set in the MainWindow property of the Application object.
• This property is set by default when the first instance of the Window class is created and the Application.Current property is set
• This setting can be overrided
• Application.Current.Windows
• The Application object’s Windows property get a list of each top-level Window
• ShutdownMode property
• OnLastWindowClose = 0 - it is the default one
• OnMainWindowClose = 1
• OnExplicitShutdown = 2
• an application can also be shut down manually by calling the Application object’s Shutdown method
• Application.Current.Shutdown()
  
• How can I create a single-instance application using WPF?

bool mutexIsNew;

using (System.Threading.Mutex m = new System.Threading.Mutex(true, uniqueName, out mutexIsNew))

{

if (mutexIsNew)

// This is the first instance. Run the application.

else

// There is already an instance running. Exit!

}

• A typical WPF application has a single UI thread and a render thread.
• The render thread is an implementation detail that is never directly exposed to developers. It runs in the background and handles low-level tasks such as composition
• DispatcherObject defines a Dispatcher property (of type Dispatcher) containing several overloads of Invoke (a synchronous call) and BeginInvoke (an asynchronous call).

ApplicationSettingsBase

• it can be used to manage user and application settings between application sessions
• supports data change notifications
• we can bind to settings data just like any other data
• 
  <Window ... >
  ...
  <TextBlock ...
  Text="{Binding Path=LastView,
  Source={x:Static local:Properties.Settings.Default}}" />
  ...
  </Window>
  
  
•