My.Application.UnhandledException Event

Visual Basic Language Reference

Updated: July 2008

Occurs when the application encounters an unhandled exception.

' Usage
Public Sub Me_UnhandledException( _
   ByVal sender As Object, _
   ByVal e As UnhandledExceptionEventArgs _
) Handles Me.UnhandledException
End Sub
' Declaration
Public Event UnhandledException( _
   ByVal sender As Object, _
   ByVal e As UnhandledExceptionEventArgs _
)

Parameters

sender: The Object that raised the event.
e: An UnhandledExceptionEventArgs object that contains the unhandled exception and additional information.

Remarks

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, so 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:

With a project selected in Solution Explorer, click Properties on the Project menu.
Click the Application tab.
Click the View Application Events button to open the Code Editor.

For more information, see How to: Handle Application Events (Visual Basic).

Note:
The Visual Basic compiler prevents applications that are built for debugging from raising this event, to allow 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 on building applications for debugging, see /debug (Visual Basic).

Note:

The Visual Basic compiler prevents applications that are built for debugging from raising this event, to allow 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 on building applications for debugging, see /debug (Visual Basic).

Tasks

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

To	See
Use the events provided by the Visual Basic Application Model to run code	How to: Run Code When the Application Starts or Ends
Log unhandled exceptions	How to: Log Exceptions in Visual Basic

Example

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

Visual Basic

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

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 How to: Handle Application Events (Visual Basic).

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

Requirements

Namespace: Microsoft.VisualBasic.ApplicationServices

Class: WindowsFormsApplicationBase

Assembly: Visual Basic Runtime Library (in Microsoft.VisualBasic.dll)

Availability by Project Type

Project type	Available
Windows Application	Yes
Class Library	No
Console Application	No
Windows Control Library	No
Web Control Library	No
Windows Service	No
Web Site	No

Permissions

The following permissions may be necessary:

Permission	Description
SecurityPermission	Controls the ability to add an event handler for this event. Associated enumeration: SecurityPermissionFlag..::.ControlAppDomain.

For more information, see Code Access Security and Requesting Permissions.

Concepts

Overview of the Visual Basic Application Model

Reference

My.Application Object

Microsoft.VisualBasic.ApplicationServices..::.UnhandledExceptionEventArgs

Change History

Date	History	Reason
July 2008	Revised information about setting the UnhandledException event handler in the "Remarks" section.	Content bug fix.

Date

History

Reason

July 2008

Revised information about setting the UnhandledException event handler in the "Remarks" section.

Content bug fix.