A Windows Presentation Foundation (WPF) application that has one or more open windows deactivates (stops being the foreground application) when a user does the following:

• Switches to another application by using ALT+TAB or by using Task Manager.

• Clicks the taskbar button for a window in another application.

Applications that need to detect deactivation can handle the Deactivated 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 Deactivated and Activated events to determine which state it's in. For more information, including an example that illustrates this dependency, see Application Activation and Deactivation Sample.

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

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

<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;
        }
    }
}

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

.NET Framework

Reference