Application.Startup Event

Microsoft Silverlight will reach end of support after October 2021. Learn more.

Occurs when an application is started.

Namespace:  System.Windows
Assembly:  System.Windows (in System.Windows.dll)


Public Event Startup As StartupEventHandler
public event StartupEventHandler Startup
<Application Startup="eventhandler"/>


A typical Silverlight application may perform a variety of initialization tasks when it starts up, including:

  • Processing initialization retrieved from the InitParams property of the StartupEventArgs object that is passed to the Startup event handler.

  • Showing the application's main application UI by setting the RootVisual property.

  • Initialize application-scoped properties by setting custom properties implemented by the application class.

Additionally, Startup is an appropriate location for performing other common initialization tasks, loading data from the previous application session, and logging.


The following code shows how to handle the Startup event.

Partial Public Class App
    Inherits Application

    public Sub New()
    End Sub

    Private Sub Application_Startup(ByVal o As Object, _
        ByVal e As StartupEventArgs) Handles Me.Startup

        ' Detect when the application starts up.

    End Sub

End Class
using System.Windows; // Application, StartupEventArgs

namespace SilverlightApplication
    public partial class App : Application
        public App()
            this.Startup += this.Application_Startup;

        private void Application_Startup(object sender, StartupEventArgs e)
            // Detect when the application starts up.

Version Information


Supported in: 5, 4, 3

Silverlight for Windows Phone

Supported in: Windows Phone OS 7.1, Windows Phone OS 7.0


For a list of the operating systems and browsers that are supported by Silverlight, see Supported Operating Systems and Browsers.