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POWPF OpenFileDialog Suppresses Exception
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copied!<p>Perhaps I'm using the <code>OpenFileDialog</code> incorrectly, but I've found that unhandled exceptions are being suppressed whenever the <code>OpenFileDialog</code> is used and the result is passed into my model. </p> <p>Typically I'll hook ino the <code>AppDomain.CurrentDomain.UnhandledException</code> event to handle any unhandled exceptions, but any exceptions being raised after using the <code>OpenFileDialog</code> are swallowed whole.</p> <p>The following is an example to reproduce this behavior. If you run the example, you'll see that the exceptions being thrown in the code behind and the <code>ShellModel.ThrowException</code> property are correctly caught by the <code>UnHandledException</code> handler in the App.xaml.cs. However, the exception being thrown in the <code>ShellModel.OpenFile</code> property after using the <code>OpenFileDialog</code> is being suppressed.</p> <p>Why would these exceptions be suppressed?</p> <p><strong>App.xaml.cs</strong></p> <pre><code>using System; using System.Text; using System.Windows; namespace ExceptionTest { /// <summary> /// Interaction logic for App.xaml /// </summary> public partial class App : Application { protected override void OnStartup( StartupEventArgs e ) { base.OnStartup( e ); AppDomain.CurrentDomain.UnhandledException += OnUnhandledException; } private void OnUnhandledException( object sender, UnhandledExceptionEventArgs e ) { var ex = e.ExceptionObject as Exception; if( ex == null ) { MessageBox.Show( string.Format( "Null Exception: {0}", e ) ); return; } var sb = new StringBuilder(); sb.AppendLine( "An unhandled exception was encountered. Terminating now." ); sb.AppendLine(); sb.AppendLine( "Exception:" ); sb.AppendLine( ex.Message ); MessageBox.Show( sb.ToString(), "Whoops...", MessageBoxButton.OK, MessageBoxImage.Error ); Environment.Exit( 1 ); } } } </code></pre> <p><strong>Shell.xaml</strong></p> <pre><code><Window x:Class="ExceptionTest.Shell" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" xmlns:Model="clr-namespace:ExceptionTest" Title="Exception Test" Height="350" Width="350" WindowStartupLocation="CenterScreen"> <Window.DataContext> <Model:ShellModel x:Name="Model" /> </Window.DataContext> <StackPanel Orientation="Vertical" VerticalAlignment="Stretch"> <Button Click="OnCodeBehind" Margin="20" Content="Exception from code behind" Height="25" Width="250" /> <Button Click="OnThrowExeption" Margin="20" Content="Exception from Model" Height="25" Width="250" /> <Button Click="OnFindFile" Margin="20" Content="Exception from OpenFileDialog" Height="25" Width="250" /> <Label Content="{Binding OpenFile, Mode=TwoWay}" x:Name="OpenFile" Height="28" HorizontalAlignment="Left" VerticalAlignment="Top" Width="Auto" /> </StackPanel> </Window> </code></pre> <p><strong>Shell.xaml.cs / Model</strong></p> <pre><code>using System; using System.ComponentModel; using System.IO; using System.Reflection; using System.Windows; using Microsoft.Win32; namespace ExceptionTest { /// <summary> /// Interaction logic for MainWindow.xaml /// </summary> public partial class Shell : Window { private OpenFileDialog OpenDialog { get; set; } public Shell() { InitializeComponent(); OpenDialog = new OpenFileDialog(); string path = new Uri( Assembly.GetExecutingAssembly().CodeBase ).LocalPath; OpenDialog.InitialDirectory = Path.GetDirectoryName( path ); OpenDialog.Multiselect = false; OpenDialog.Title = "Find File"; OpenDialog.RestoreDirectory = true; } private void OnCodeBehind( object sender, RoutedEventArgs e ) { throw new Exception( "Exception from Code Behind." ); } private void OnThrowExeption( object sender, RoutedEventArgs e ) { Model.ThrowException = "Test"; e.Handled = true; } private void OnFindFile( object sender, RoutedEventArgs e ) { OpenDialog.ShowDialog( this ); string fileName = OpenDialog.FileName; if( !string.IsNullOrEmpty( fileName ) ) { OpenDialog.InitialDirectory = Path.GetDirectoryName( fileName ); OpenFile.Content = fileName; } } } public class ShellModel : INotifyPropertyChanged { private string _throwException; public string ThrowException { get { return _throwException; } set { _throwException = value; NotifyPropertyChanged( "ThrowException" ); throw new Exception( "Exception from Model." ); } } private string _openFile; public string OpenFile { get { return _openFile; } set { _openFile = value; NotifyPropertyChanged( "OpenFile" ); throw new Exception( "Exception from Model after using OpenFileDialog." ); } } public event PropertyChangedEventHandler PropertyChanged; private void NotifyPropertyChanged( String info ) { if( PropertyChanged != null ) { PropertyChanged( this, new PropertyChangedEventArgs( info ) ); } } } } </code></pre> <h2>Resolution</h2> <p>As noted in the answer, this isn't an OpenFileDialog issues, rather its a data binding issue.</p> <p>Bradley's answer and Hans possible duplicate link pointed to some great information. The links/articles didn't quite provide the resolution I came up with, re: I found there was another exception I could hook into: <code>AppDomain.CurrentDomain.FirstChanceException</code></p> <p>Here's a modified version of my <code>App.Xaml.cs</code>:</p> <pre><code>protected override void OnStartup( StartupEventArgs e ) { base.OnStartup( e ); AppDomain.CurrentDomain.UnhandledException += OnUnhandledException; // The FirstChanceException will catch binding errors AppDomain.CurrentDomain.FirstChanceException += OnFirstChanceException; } private void OnFirstChanceException( object sender, FirstChanceExceptionEventArgs e ) { // do stuff } </code></pre> <p>The binding errors are now caught!</p>

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