On Error for windows application

Question

Is there any global event in .NET Windows Forms and WPF applications, equivalent to On_Error in ASP.NET - Global.aspx?

Answer 1

Application.ThreadException

This event is raised whenever an unhandled exception occurs.

I mostly subscribe to this event, and, in the eventhandler, I log the Exception that has occured, or display a MessageBox which displays that something has gone wrong.

Answer 2

As mentioned by others, you can use Application.ThreadException

For user friendly Exception Handling, check this link.

[STAThread] static void Main() {
  Application.ThreadException += new System.Threading.ThreadExceptionEventHandler(Application_ThreadException);
  Application.Run(new Form1());
}

private void button1_Click(object sender, System.EventArgs e) {
  throw new Exception("Whoops"); 
}

private static void Application_ThreadException(object sender, System.Threading.ThreadExceptionEventArgs e) {
  MessageBox.Show(e.Exception.Message); 
}

Answer 3

There are basically two options to trap unhandled exceptions globally:

• Application.ThreadException for Windows.Forms (as already pointed out by others)
• AppDomain.CurrentDomain.UnhandledException

The following sample program shows how to use the UnhandledException event in C#:

class Program
{
    static void Main(string[] args)
    {
        AppDomain.CurrentDomain.UnhandledException += new UnhandledExceptionEventHandler(CurrentDomain_UnhandledException);
    }

    static void CurrentDomain_UnhandledException(object sender, UnhandledExceptionEventArgs e)
    {
        Exception ex = (Exception)e.ExceptionObject;
        Console.WriteLine("Unhandled exception!!");
        Console.WriteLine(ex.InnerException.Message);
    }
}

Answer 4

In addition to Application.ThreadException, you should handle AppDomain.CurrentDoman.UnhandledException. The relevant snippet from one of my program.cs files looks like this:

Application.ThreadException += new ThreadExceptionEventHandler(AppExceptionHandler.Application_ThreadException);
Application.SetUnhandledExceptionMode(UnhandledExceptionMode.CatchException);
AppDomain.CurrentDomain.UnhandledException += new UnhandledExceptionEventHandler(AppExceptionHandler.CurrentDomain_UnhandledException);

Edited to add: Here's a good article that explains further.

Answer 5

For both ASP.NET and WinForms apps, there is the AppDomain UnhandledException event:

AddHandler AppDomain.CurrentDomain.UnhandledException, AddressOf UnhandledException

In this handler, you can perform any custom logging/recovery needed:

Private Sub UnhandledException(ByVal sender As Object, ByVal e As System.UnhandledExceptionEventArgs)
    Console.WriteLine(vbCrLf & "Unhandled exception:" & vbCrLf & e.ExceptionObject.ToString)
End Sub

Please note that you're not catching or handling the exception in this case: you're only receiving a notification event. Unless you end the application in your event handler, the exception will be propagated to the higher-level fault handler, which for WinForms apps will usually be in the operating system, leading to the familiar "This application has..." crash dialog.