WindowsFormsApplicationBase::UnhandledException Event

.NET Framework (current version)

Occurs when the application encounters an unhandled exception.

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

Syntax

C++

public:
event UnhandledExceptionEventHandler^ UnhandledException {
	void add(UnhandledExceptionEventHandler^ value);
	void remove(UnhandledExceptionEventHandler^ value);
}

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

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 Application Page, Project Designer (Visual Basic).

Note
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).

Note

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

Examples

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

Security

SecurityPermission

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

Version Information

.NET Framework
Available since 2.0