AppDomain.CurrentDomain.UnhandledException not firing without debugging

Question

I have a .NET program with an event handler bound to Application.CurrentDomain.UnhandledException. When running the program with debugging, this event fires when an unhandled exception is thrown. However, when running without debugging, the event does not fire.

What is my problem?

Thanks, Andrew

Answer 1

I assume you have not set the correct exception handling mode using Application.SetUnhandledExceptionMode() - just set it to UnhandledExceptionMode.ThrowException.

UPDATE

I just wrote a small test application and found nothing to work unexscpected. Could you try to reproduce your error with this test code?

using System;
using System.Drawing;
using System.Threading;
using System.Windows.Forms;

namespace ConsoleApplication
{
    public static class Program
    {
        static void Main()
        {
            AppDomain.CurrentDomain.UnhandledException += AppDomain_UnhandledException;

            Application.ThreadException += Application_ThreadException;
            Application.SetUnhandledExceptionMode(UnhandledExceptionMode.CatchException);

            Application.Run(new TestForm());

            throw new Exception("Main");
        }

        static void Application_ThreadException(Object sender, ThreadExceptionEventArgs e)
        {
            MessageBox.Show(e.Exception.Message, "Application.ThreadException");
        }

        static void AppDomain_UnhandledException(Object sender, UnhandledExceptionEventArgs e)
        {
            MessageBox.Show(((Exception)e.ExceptionObject).Message, "AppDomain.UnhandledException");
        }
    }

    public class TestForm : Form
    {
        public TestForm()
        {
            this.Text = "Test Application";
            this.ClientSize = new Size(200, 60);
            this.MinimumSize = this.Size;
            this.MaximumSize = this.Size;
            this.StartPosition = FormStartPosition.CenterScreen;

            Button btnThrowException = new Button();

            btnThrowException.Text = "Throw";
            btnThrowException.Location = new Point(0, 0);
            btnThrowException.Size = new Size(200, 30);
            btnThrowException.Click += (s, e) => { throw new Exception("Throw"); };

            Button btnThrowExceptionOnOtherThread = new Button();

            btnThrowExceptionOnOtherThread.Text = "Throw on other thread";
            btnThrowExceptionOnOtherThread.Location = new Point(0, 30);
            btnThrowExceptionOnOtherThread.Size = new Size(200, 30);
            btnThrowExceptionOnOtherThread.Click += (s, e) => new Thread(() => { throw new Exception("Other thread"); }).Start();

            this.Controls.Add(btnThrowException);
            this.Controls.Add(btnThrowExceptionOnOtherThread);
        }
    }
}

Answer 2

Maybe the exception is thrown within a separate thread in your application. We've seen the problem of an application just "stopping" (means: one second it's there, the other second it's gone) when an unhandled exception occurs within a thread. In that case, not even the unhandled exception handler got triggered.