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WindowsFormsApplicationBase.UnhandledException Event

Occurs when the application encounters an unhandled exception.

Namespace:  Microsoft.VisualBasic.ApplicationServices
Assembly:  Microsoft.VisualBasic (in Microsoft.VisualBasic.dll)

public event UnhandledExceptionEventHandler UnhandledException

An application raises the UnhandledException event when it encounters an unhandled exception. This event is part of the Visual Basic Application model. For more information, see Overview of the Visual Basic Application Model.

You can use the Exception property of the e parameter to access the unhandled exception that caused this event.

You can use the ExitApplication property of the e parameter to control whether the application exits. By default, ExitApplication is True. Therefore, the application exits after completing the UnhandledException event handler. You can set the value to False in the UnhandledException event handler to keep the application running, and have it return to a waiting state.

The code for the UnhandledException event handler is stored in the ApplicationEvents.vb file, which is hidden by default.

To access the Code Editor window for application events

  1. With a project selected in Solution Explorer, click Properties on the Project menu.

  2. Click the Application tab.

  3. Click the View Application Events button to open the Code Editor.

For more information, see Application Page, Project Designer (Visual Basic).

NoteNote

The Visual Basic compiler prevents applications that are built for debugging from raising this event, to enable a debugger to handle the unhandled exceptions. This means that if you are testing your application by running it under the Visual Studio Integrated Development Environment debugger, your UnhandledException event handler will not be called. For more information about building applications for debugging, see /debug (Visual Basic).

Tasks

The following table lists examples of tasks that involve the My.Application.UnhandledException event.

To

See

Log unhandled exceptions

How to: Log Exceptions in Visual Basic

Availability by Project Type

Project type

Available

Windows Forms Application

Yes

Class Library

No

Console Application

No

Windows Forms Control Library

No

Web Control Library

No

Windows Service

No

Web Site

No

This example uses the My.Application.UnhandledException event to log any unhandled exceptions.

You must enter the code in the Code Editor window for application events. To access this window, follow the procedure found in this topic's Remarks section. For more information, see Application Page, Project Designer (Visual Basic).

Because the UnhandledException event is not raised when a debugger is attached to the application, you have to run this example outside the Visual Studio Integrated Development Environment.

Private Sub MyApplication_UnhandledException( 
    ByVal sender As Object, 
    ByVal e As Microsoft.VisualBasic.ApplicationServices.UnhandledExceptionEventArgs 
) Handles Me.UnhandledException

    My.Application.Log.WriteException(e.Exception, 
        TraceEventType.Critical, 
        "Unhandled Exception.")
End Sub

.NET Framework

Supported in: 4.5.2, 4.5.1, 4.5, 4, 3.5, 3.0, 2.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Windows 8.1, Windows Server 2012 R2, Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)

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

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