Exceptions thrown during Set operation on Property do not get caught

Question

When I try to run a function inside the Set property clause, any exception thrown never gets into my global exception handler. I do not understand why this is happening. Here is my code (3 parts)

MainWindow.xaml.cs

public partial class MainWindow : Window { public MainWindow() { InitializeComponent(); DataContext = new ViewModel_(); } } public class ViewModel_ : INotifyPropertyChanged { public ViewModel_() { } public string Texting { get { return _Texting; } set { _Texting = value; OnPropertyChanged("Texting"); throw new Exception("BAM!"); } } private string _Texting; public event PropertyChangedEventHandler PropertyChanged; protected void OnPropertyChanged(string propertyName) { PropertyChangedEventHandler handler = PropertyChanged; if (handler != null) handler(this, new PropertyChangedEventArgs(propertyName)); } } 

MainWindow.xaml

 <Window x:Class="TestExceptionHandling.MainWindow" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" Title="MainWindow" Height="350" Width="525"> <Grid> <TextBox Text="{Binding Path=Texting, UpdateSourceTrigger=PropertyChanged}" /> </Grid> 

App.xaml.cs (where the global exception handler is used)

 public partial class App : Application { public App() { AppDomain.CurrentDomain.UnhandledException += CurrentDomain_UnhandledException; } void CurrentDomain_UnhandledException(object sender, UnhandledExceptionEventArgs e) { MessageBox.Show("SOMETHING IS WRONG!"); } } 

Answer 1

As Bob Horn says, binding properties are not exploded if they come from the target element (TextBox), that is, from your view. Look in your output window, you will see a message something like this:

 A first chance exception of type 'System.Exception' occurred in WpfApplication4.exe An exception of type 'System.Exception' occurred in WpfApplication4.exe but was not handled in user code System.Windows.Data Error: 8 : Cannot save value from target back to source. BindingExpression:Path=Name; DataItem='VM' (HashCode=28331431); target element is 'TextBox' (Name=''); target property is 'Text' (type 'String') Exception:'System.Exception: BAM! 

But, try setting the same property from your ViewModel constructor , the application will certainly explode.

As a side note, this is not valid for all exceptions, try doing this -

 public string Texting { get { return _Texting; } set { _Texting = value; OnPropertyChanged("Texting"); throw new StackOverflowException("BAM!"); } } 

This will certainly catch up with your global exception handler, since the application cannot be run in StackOverflow mode.