How do I gracefully handle XamlParseExceptions?

Question

If a control that is dynamically loaded as part of a template has an error, it causes a XamlParseException which crashes the entire application.
I can hook into the Application.DispatcherUnhandledException event, but setting Handled to true on the DispatcherUnhandledExceptionEventArgs argument does not disable the problematic control. As a result, WPF tries again to apply the template, causing the
error to be thrown once more, resulting in an infinite loop.
Is there any way to disable the problematic control so that it stops trying to render?
Here is how to reproduce this scenario:
1. Create a WPF application.
2. Add a Window called "Dialog1" and a UserControl called "UserControl1".
3. Add the following code to each file (namespaces and root XAML elements left out):
App.xaml.cs:
(Also add the following namespace reference to the top: using System.Windows.Threading;)
public partial class App : Application
protected override void OnStartup(StartupEventArgs e)
base.OnStartup(e);
DispatcherUnhandledException += OnDispatcherUnhandledException;
private void OnDispatcherUnhandledException(object sender, DispatcherUnhandledExceptionEventArgs e)
e.Handled = true;
Dialog1.xaml:
(Also add the following namespace reference: xmlns:local="clr-namespace:your app namespace")
<StackPanel>
<Button Content="Cause XamlParseException" Click="Button_Click" />
<ListBox ItemsSource="{Binding Mode=OneWay}">
<ListBox.ItemTemplate>
<DataTemplate>
<local:UserControl1 />
</DataTemplate>
</ListBox.ItemTemplate>
</ListBox>
</StackPanel>
Dialog1.xaml.cs:
public partial class Dialog1 : Window
public Dialog1()
InitializeComponent();
private void Button_Click(object sender, RoutedEventArgs e)
var list = new object[1];
list[0] = new object();
DataContext = list;
MainWindow.xaml:
<StackPanel>
<Button Content="Show Dialog" Click="Button_Click" />
</StackPanel>
MainWindow.xaml.cs:
public partial class MainWindow : Window
public MainWindow()
InitializeComponent();
private void Button_Click(object sender, RoutedEventArgs e)
var dlg = new Dialog1();
dlg.ShowDialog();
UserControl1.xaml.cs:
public partial class UserControl1 : UserControl
public UserControl1()
InitializeComponent();
throw new Exception();
Run the solution, click the "Show Dialog" button, and then click the "Cause XamlParseException" button. This will cause the exception to be thrown repeatedly.

Answer 1

>>Is there any way to disable the problematic control so that it stops trying to render?
Not apart from catching and handling the exception in your code where it is being raised:
public UserControl1()
InitializeComponent();
try
throw new Exception();
catch (Exception ex)
There are some exceptions that you can't recover from and setting the Handled property to true in this case just causes the same exception to ge thrown over and over again.
The most meaningful thing you can do when an DispatcherUnhandledException occurs is to log the exception and then terminate the application:
private void OnDispatcherUnhandledException(object sender, DispatcherUnhandledExceptionEventArgs e)
Exception ex = e.Exception;
//log the exception...
Environment.Exit(1);
Setting the Handled property of the DispatcherUnhandledExceptionEventArgs to true and trying to continue on like nothing ever happened may leave your application in an undefined state and is rarely a good idea.
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