Application.Activated Event (System.Windows)

Activated Event

.NET Framework Class Library

Application..::.Activated Event

Occurs when an application becomes the foreground application.

Namespace: System.Windows
Assembly: PresentationFramework (in PresentationFramework.dll)
XMLNS for XAML: http://schemas.microsoft.com/winfx/2006/xaml/presentation, http://schemas.microsoft.com/netfx/2007/xaml/presentation

Syntax

Visual Basic (Declaration)

Public Event Activated As EventHandler

Visual Basic (Usage)

Dim instance As Application
Dim handler As EventHandler

AddHandler instance.Activated, handler

public event EventHandler Activated

Visual C++

public:
 event EventHandler^ Activated {
    void add (EventHandler^ value);
    void remove (EventHandler^ value);
}

JScript

JScript does not support events.

XAML Attribute Usage

<object Activated="EventHandler" .../>

Remarks

A Windows Presentation Foundation (WPF) application that has one or more open windows is activated (becomes the foreground application) when one of the windows is activated for the first time since the application was launched, or when one of the windows is activated while the application is inactive: Specifically, activation occurs when:

An application opens its first window.
A user switches to the application by using ALT+TAB or by using Task Manager.
A user clicks the taskbar button for one of the windows in an application.

Applications that need to detect when they activate can handle the Activated event.

After an application is first activated, it may be deactivated and reactivated many times during its lifetime. If an application's behavior or state depends on its activation state, it can handle both Activated and Deactivated events to determine which activation state it's in. For more information, including an example that illustrates this dependency, see Application Activation and Deactivation Sample.

Once an application becomes active, Activated will not be raised again until the application is deactivated, irrespective of how many windows within an application are activated while the application is active.

Activated is not raised for XAML browser applications (XBAPs).

Examples

The following example shows how to detect when a standalone application activates and deactivates.

XAML

<Application 
  xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
  xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
  x:Class="SDKSample.App"
  StartupUri="MainWindow.xaml"
  Activated="App_Activated" 
  Deactivated="App_Deactivated" />

using System; // EventArgs
using System.Windows; // Application

namespace SDKSample
{
    public partial class App : Application
    {
        bool isApplicationActive;

        void App_Activated(object sender, EventArgs e)
        {
            // Application activated
            this.isApplicationActive = true;
        }

        void App_Deactivated(object sender, EventArgs e)
        {
            // Application deactivated
            this.isApplicationActive = false;
        }
    }
}

Platforms

Windows 7, Windows Vista, Windows XP SP2, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003

The .NET Framework and .NET Compact Framework do not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

Version Information

.NET Framework

Supported in: 3.5, 3.0

Reference

Application Class

Application Members

System.Windows Namespace

OnActivated

Deactivated