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Application class

Applies to Windows and Windows Phone

Encapsulates the app and its available services.

Inheritance

Object
  Application

Syntax


public class Application

Attributes

[MarshalingBehavior(Agile)]
[Threading(Both)]
[Version(0x06020000)]
[WebHostHidden()]

Members

The Application class has these types of members:

Constructors

The Application class has these constructors.

ConstructorDescription
Application Initializes a new instance of the Application class.

 

Events

The Application class has these events.

EventDescription
Resuming Occurs when the application transitions from Suspended state to Running state.
Suspending Occurs when the application transitions to Suspended state from some other state.
UnhandledException Occurs when an exception can be handled by app code, as forwarded from a native-level Windows Runtime error. Apps can mark the occurrence as handled in event data.

 

Methods

The Application class has these methods. It also inherits methods from the Object class.

MethodDescription
Exit Shuts down the app.
LoadComponent(Object, Uri) Loads a XAML file that is located at the specified relative location, and converts it to an instance of the object that is specified by the root element of the XAML file.
LoadComponent(Object, Uri, ComponentResourceLocation) Loads a XAML file that is located at the specified relative location, and converts it to an instance of the object that is specified by the root element of the XAML file.
OnActivated Invoked when the application is activated by some means other than normal launching.
OnCachedFileUpdaterActivated Invoked when the application is activated due to an activation contract with ActivationKind as CachedFileUpdater.
OnFileActivated Invoked when the application is activated through file-open.
OnFileOpenPickerActivated Invoked when the application is activated through file-open dialog association.
OnFileSavePickerActivated Invoked when the application is activated through file-save dialog association.
OnLaunched Invoked when the application is launched. Override this method to perform application initialization and to display initial content in the associated Window.
OnSearchActivated Invoked when the application is activated through a search association.
OnShareTargetActivated Invoked when the application is activated through sharing association.
OnWindowCreated Invoked when the application creates a window.
Start Provides the entry point and requests initialization of the application. Use the callback to instantiate the Application class.

 

Properties

The Application class has these properties.

PropertyAccess typeDescription

Current

Read-onlyGets the Application object for the current application.

DebugSettings

Read-onlyGets an object that declares how the app behaves when run in a debug environment.

RequestedTheme

Read/writeGets or sets a value that determines the light-dark preference for the overall theme of an app.

Resources

Read/writeGets a collection of application-scoped resources, such as styles, templates, and brushes.

 

Remarks

The Application class encapsulates an app and provides the following services:

  • app entry point, particularly for various activation contracts
  • app lifetime management
  • app-scoped resources
  • unhandled exception detection

The Application object is typically provided in the initial XAML for App.xaml. The default project templates in Visual Studio generate an App class that derives from Application and provides an entry point where you can add initialization code.

The App class associates itself with the corresponding XAML by calling the generated InitializeComponent method in its constructor. You can add additional initialization code to the App constructor, but you will typically only add code to associate handlers to Application events. For other initialization code, you should override one or more initialization methods such as OnLaunched.

The system handles app lifetime by suspending your app whenever the user switches to another app or to the desktop, and resuming your app whenever the user switches back to it. However, the system can also terminate your app while it is suspended in order to free up resources. You should handle the Suspending event to save your app state in case of termination, and override the OnLaunched method to restore your app state. You should handle the Resuming event only if you need to refresh any displayed content that might have changed while the app is suspended. You do not need to restore other app state when the app resumes.

Because of its position in the application model, codegen, and activation sequence, Application has some restrictions on its XAML usage:

  • Other than the xmlns declarations and x:Class, no other attribute can appear on the Application root tag.
  • Don't attempt to change x:Class values that come from the project template App.xaml pages, there are additional dependencies on using that naming scheme that exist in the build actions.
  • Don't wire the Application event handlers in XAML. All event wiring should be done in code (usually in the constructor). Also, you generally use method overrides rather than event syntax for an event (for example, you override OnActivated to respond to that phase of the application life cycle.)
  • The only expected properties on an Application instance in XAML is the set of elements to populate the Application.Resources property, using a XAML property element usage. For more info, see Resources.

To provide general error handling for any exceptions that your app code doesn't catch, handle the UnhandledException event.

Note  The Application main file must be named App.xaml.

Requirements

Minimum supported client

Windows 8 [Windows Store apps only]

Minimum supported server

Windows Server 2012 [Windows Store apps only]

Minimum supported phone

Windows Phone 8.1 [Windows Runtime apps only]

Namespace

Windows.UI.Xaml
Windows::UI::Xaml [C++]

Metadata

Windows.winmd

See also

How to activate an app
How to suspend an app
How to resume an app
Window

 

 

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