Application.DispatcherUnhandledException Event
Definition
Important
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Occurs when an exception is thrown by an application but not handled.
public:
event System::Windows::Threading::DispatcherUnhandledExceptionEventHandler ^ DispatcherUnhandledException;public event System.Windows.Threading.DispatcherUnhandledExceptionEventHandler DispatcherUnhandledException;member this.DispatcherUnhandledException : System.Windows.Threading.DispatcherUnhandledExceptionEventHandler Public Custom Event DispatcherUnhandledException As DispatcherUnhandledExceptionEventHandler Event Type
Examples
The following example shows how to process unhandled exceptions by handling the DispatcherUnhandledException event.
using System.Windows;
using System.Windows.Threading;
namespace SDKSample
{
public partial class App : Application
{
void App_DispatcherUnhandledException(object sender, DispatcherUnhandledExceptionEventArgs e)
{
// Process unhandled exception
// Prevent default unhandled exception processing
e.Handled = true;
}
}
}
Imports System.Windows
Imports System.Windows.Threading
Namespace SDKSample
Partial Public Class App
Inherits Application
Private Sub App_DispatcherUnhandledException(ByVal sender As Object, ByVal e As DispatcherUnhandledExceptionEventArgs)
' Process unhandled exception
' Prevent default unhandled exception processing
e.Handled = True
End Sub
End Class
End Namespace
Remarks
By default, Windows Presentation Foundation catches unhandled exceptions, notifies users of the exception from a dialog box (from which they can report the exception), and automatically shuts down an application.
However, if an application needs to perform custom unhandled exception processing from a centralized location, you should handle DispatcherUnhandledException.
DispatcherUnhandledException is raised by an Application for each exception that is unhandled by code running on the main UI thread.
If an exception is not handled on either a background UI thread (a thread with its own Dispatcher) or a background worker thread (a thread without a Dispatcher), the exception is not forwarded to the main UI thread. Consequently, DispatcherUnhandledException is not raised. In these circumstances, you will need to write code to do the following:
Handle exceptions on the background thread.
Dispatch those exceptions to the main UI thread.
Rethrow them on the main UI thread without handling them to allow DispatcherUnhandledException to be raised.
For more information, see the Threading Model overview.
The DispatcherUnhandledException event handler is passed a DispatcherUnhandledExceptionEventArgs argument that contains contextual information regarding the exception, including:
The exception (Exception).
The Dispatcher from which it originated (Dispatcher).
You can use this information to determine whether an exception is recoverable or not. A recoverable exception might be a FileNotFoundException, for example, while an unrecoverable exception might be a StackOverflowException, for example.
When you process an unhandled exception from DispatcherUnhandledException, and you don't want WPF to continue processing it, you need to set the Handled property to true.
Unlike the other events that Application raises, DispatcherUnhandledException does not have a matching protected virtual implementation (OnDispatcherUnhandledException). Consequently, classes that derive from Application must always register an event handler with DispatcherUnhandledException to process unhandled exceptions.
