Exception Handling Question

[Chuck Cobb]

I'm implementing a centralized exception handling routine using the
Enterprise Library Exception Management Application Block.

I trap all unhandled exceptions to one place using the following method:

// --- Create an Exception Handler for Thread Exceptions ----------------

Application.Thr eadException += new
ThreadException EventHandler(On ThreadException );

// --- Create an Exception Handler for Unhandled Exceptions -------------

AppDomain currentDomain = AppDomain.Curre ntDomain;

currentDomain.U nhandledExcepti on += new
UnhandledExcept ionEventHandler (OnUnhandledExc eption);

private static void OnThreadExcepti on(object sender,

ThreadException EventArgs t)

//
*************** *************** *************** *************** *************** ***

// Handles Normal Thread Exceptions

//
*************** *************** *************** *************** *************** ***

{

Exceptions.LogA ndReportError(t .Exception);

}

private static void OnUnhandledExce ption(object sender,

UnhandledExcept ionEventArgs args)

//
*************** *************** *************** *************** *************** ***

// Handles All Unhandled Exceptions

//
*************** *************** *************** *************** *************** ***

{

Exceptions.LogA ndReportError(a rgs.ExceptionOb ject as System.Exceptio n);

}

The problem I have is that exceptions that occur on a background thread are
not being picked up. If I do a "throw" on an exception in a background
thread it has no place to go and just disappears as an unhandled exception.
How can I pick up these exceptions without handling them in the background
thread?

Thanks,

Chuck Cobb

[Christoph Nahr]

On Fri, 21 Apr 2006 07:40:14 -0400, "Chuck Cobb"
<ch********@oxf ordcorp.com> wrote:

The problem I have is that exceptions that occur on a background thread are
not being picked up. If I do a "throw" on an exception in a background
thread it has no place to go and just disappears as an unhandled exception.
How can I pick up these exceptions without handling them in the background
thread?

What .NET version is that? Joe Duffy's "Profession al .NET Framework
2.0" states that Versions 1.0 and 1.1 used to silently swallow
unhandled exceptions on a background thread. Apparently there's
nothing you can do about that. Version 2.0 should correctly invoke
your UnhandledExcept ion handler.
--
http://www.kynosarges.de

[Christoph Nahr]

On Fri, 21 Apr 2006 15:47:55 +0200, Christoph Nahr
<ch************ @kynosarges.de> wrote:

What .NET version is that? Joe Duffy's "Profession al .NET Framework
2.0" states that Versions 1.0 and 1.1 used to silently swallow
unhandled exceptions on a background thread. Apparently there's
nothing you can do about that. Version 2.0 should correctly invoke
your UnhandledExcept ion handler.

Just found confirmation on Jeff Atwood's weblog, right here:
http://www.codinghorror.com/blog/archives/000201.html

Scroll down to a reply by Jonathan Keljo, CLR Exceptions PM:

"Just to complicate things, in v1.0 and 1.1, an unhandled exception
did not always mean that your application would die. If the unhandled
exception occurred on anything other than the main thread or a thread
that began its life in unmanaged code, the CLR ate the exception and
allowed your app to keep going. This was generally evil, because what
would often happen was, for example, that ThreadPool threads would
silently die off, one by one, until your application wasn't actually
doing any work. Figuring out the cause of this kind of failure was
nearly impossible. [...]"

"In v2.0, an unhandled exception on any thread will take down the
application. We've found that it's tremendously easier to debug
crashes than it is to debug hangs or the silent-stoppage-of-work
problem described above."
--
http://www.kynosarges.de

[Chuck Cobb]

Hi Christopher,

I am using .Net 2.0 and I can confirm that it is still swallowing exceptions
on a background thread. The code I used to test it looks like this

public static void BackgroundProce ss
{
try
{
throw new Exception("Simu lated Error");
}
catch
{
throw;
}
}

When I execute the above code, it creates the exception, goes to the catch
block and when it attempts to rethrow it using the "throw", it goes nowhere
"Christoph Nahr" <ch************ @kynosarges.de> wrote in message
news:j1******** *************** *********@4ax.c om...

On Fri, 21 Apr 2006 15:47:55 +0200, Christoph Nahr
<ch************ @kynosarges.de> wrote:

What .NET version is that? Joe Duffy's "Profession al .NET Framework
2.0" states that Versions 1.0 and 1.1 used to silently swallow
unhandled exceptions on a background thread. Apparently there's
nothing you can do about that. Version 2.0 should correctly invoke
your UnhandledExcept ion handler.

Just found confirmation on Jeff Atwood's weblog, right here:
http://www.codinghorror.com/blog/archives/000201.html

Scroll down to a reply by Jonathan Keljo, CLR Exceptions PM:

"Just to complicate things, in v1.0 and 1.1, an unhandled exception
did not always mean that your application would die. If the unhandled
exception occurred on anything other than the main thread or a thread
that began its life in unmanaged code, the CLR ate the exception and
allowed your app to keep going. This was generally evil, because what
would often happen was, for example, that ThreadPool threads would
silently die off, one by one, until your application wasn't actually
doing any work. Figuring out the cause of this kind of failure was
nearly impossible. [...]"

"In v2.0, an unhandled exception on any thread will take down the
application. We've found that it's tremendously easier to debug
crashes than it is to debug hangs or the silent-stoppage-of-work
problem described above."
--
http://www.kynosarges.de

[Christoph Nahr]

On Fri, 21 Apr 2006 10:51:17 -0400, "Chuck Cobb"
<ch********@oxf ordcorp.com> wrote:

When I execute the above code, it creates the exception, goes to the catch
block and when it attempts to rethrow it using the "throw", it goes nowhere

That's very strange. The UnhandledExcept ion handler doesn't get
triggered at all? Does it work if you just throw the exception,
outside of a try/catch block? Maybe the rethrow is the culprit.

In any case, that looks very much like a bug to me. Could you try
isolating a test case and post it here, or post a link to it?
--
http://www.kynosarges.de

[Willy Denoyette [MVP]]

ThreadException is meant to handle unhandled exceptions on the UI thread,
you need to install an UnhandledExcept ionEventHandler to handle unhandled
excptions on auxiliary threads.

Willy.

"Chuck Cobb" <ch********@oxf ordcorp.com> wrote in message
news:eT******** ******@TK2MSFTN GP04.phx.gbl...
| I'm implementing a centralized exception handling routine using the
| Enterprise Library Exception Management Application Block.
|
| I trap all unhandled exceptions to one place using the following method:
|
| // --- Create an Exception Handler for Thread Exceptions ----------------
|
| Application.Thr eadException += new
| ThreadException EventHandler(On ThreadException );
|
| // --- Create an Exception Handler for Unhandled Exceptions -------------
|
| AppDomain currentDomain = AppDomain.Curre ntDomain;
|
| currentDomain.U nhandledExcepti on += new
| UnhandledExcept ionEventHandler (OnUnhandledExc eption);
|
|
|
| private static void OnThreadExcepti on(object sender,
|
| ThreadException EventArgs t)
|
| //
|
*************** *************** *************** *************** *************** ***
|
| // Handles Normal Thread Exceptions
|
| //
|
*************** *************** *************** *************** *************** ***
|
| {
|
| Exceptions.LogA ndReportError(t .Exception);
|
| }
|
|
|
| private static void OnUnhandledExce ption(object sender,
|
| UnhandledExcept ionEventArgs args)
|
| //
|
*************** *************** *************** *************** *************** ***
|
| // Handles All Unhandled Exceptions
|
| //
|
*************** *************** *************** *************** *************** ***
|
| {
|
| Exceptions.LogA ndReportError(a rgs.ExceptionOb ject as System.Exceptio n);
|
| }
|
| The problem I have is that exceptions that occur on a background thread
are
| not being picked up. If I do a "throw" on an exception in a background
| thread it has no place to go and just disappears as an unhandled
exception.
| How can I pick up these exceptions without handling them in the background
| thread?
|
| Thanks,
|
| Chuck Cobb
|
|

[Chuck Cobb]

I have an UhandledExcepti onEventHandler installed in the main thread, but it
doesn't seem to be picking up exceptions that originate in another thread.
I've tried installing it in the other thread and it still doesn't seem to be
picking up the exception.

"Willy Denoyette [MVP]" <wi************ *@telenet.be> wrote in message
news:ep******** ******@TK2MSFTN GP04.phx.gbl...

ThreadException is meant to handle unhandled exceptions on the UI thread,
you need to install an UnhandledExcept ionEventHandler to handle unhandled
excptions on auxiliary threads.

Willy.

"Chuck Cobb" <ch********@oxf ordcorp.com> wrote in message
news:eT******** ******@TK2MSFTN GP04.phx.gbl...
| I'm implementing a centralized exception handling routine using the
| Enterprise Library Exception Management Application Block.
|
| I trap all unhandled exceptions to one place using the following method:
|
| // --- Create an Exception Handler for Thread
Exceptions ----------------
|
| Application.Thr eadException += new
| ThreadException EventHandler(On ThreadException );
|
| // --- Create an Exception Handler for Unhandled
Exceptions -------------
|
| AppDomain currentDomain = AppDomain.Curre ntDomain;
|
| currentDomain.U nhandledExcepti on += new
| UnhandledExcept ionEventHandler (OnUnhandledExc eption);
|
|
|
| private static void OnThreadExcepti on(object sender,
|
| ThreadException EventArgs t)
|
| //
|
*************** *************** *************** *************** *************** ***
|
| // Handles Normal Thread Exceptions
|
| //
|
*************** *************** *************** *************** *************** ***
|
| {
|
| Exceptions.LogA ndReportError(t .Exception);
|
| }
|
|
|
| private static void OnUnhandledExce ption(object sender,
|
| UnhandledExcept ionEventArgs args)
|
| //
|
*************** *************** *************** *************** *************** ***
|
| // Handles All Unhandled Exceptions
|
| //
|
*************** *************** *************** *************** *************** ***
|
| {
|
| Exceptions.LogA ndReportError(a rgs.ExceptionOb ject as System.Exceptio n);
|
| }
|
| The problem I have is that exceptions that occur on a background thread
are
| not being picked up. If I do a "throw" on an exception in a background
| thread it has no place to go and just disappears as an unhandled
exception.
| How can I pick up these exceptions without handling them in the
background
| thread?
|
| Thanks,
|
| Chuck Cobb
|
|

[Willy Denoyette [MVP]]

Don't know what could be wrong with your code, but herewith a complete
sample that may set you on the right track.

using System;
using System.Diagnost ics;
using System.Componen tModel;
using System.Threadin g;
using System.Windows. Forms;
namespace Whatever
{
public class Form1 : Form
{
public Form1()
{
InitializeCompo nent();
}
private void throwUI_Click(o bject sender, EventArgs e)
{
throw new Exception("Thro wn from UI thread");
}
private void throwNonUI_Clic k(object sender, EventArgs e)
{
new Thread(delegate ()
{
throw new Exception("Thro wn from Aux thread");
}).Start();
}
private System.Componen tModel.IContain er components = null;
protected override void Dispose(bool disposing)
{
if (disposing && (components != null))
{
components.Disp ose();
}
base.Dispose(di sposing);
}
private void InitializeCompo nent()
{
this.throwUI = new Button();
this.throwNonUI = new Button();
this.SuspendLay out();

this.throwUI.Lo cation = new System.Drawing. Point(12, 12);
this.throwUI.Na me = "throwUI";
this.throwUI.Si ze = new System.Drawing. Size(95, 23);
this.throwUI.Ta bIndex = 0;
this.throwUI.Te xt = "Throw on UI";
this.throwUI.Cl ick += new System.EventHan dler(this.throw UI_Click);

this.throwNonUI .Location = new System.Drawing. Point(12, 42);
this.throwNonUI .Name = "throwUI";
this.throwNonUI .Size = new System.Drawing. Size(95, 23);
this.throwNonUI .TabIndex = 0;
this.throwNonUI .Text = "Throw on non UI";
this.throwNonUI .Click += new
System.EventHan dler(this.throw NonUI_Click);

this.AutoScaleD imensions = new System.Drawing. SizeF(6F, 13F);
this.AutoScaleM ode = System.Windows. Forms.AutoScale Mode.Font;
this.ClientSize = new System.Drawing. Size(283, 150);

this.Controls.A dd(this.throwUI );
this.Controls.A dd(this.throwNo nUI);
this.Name = "Form1";
this.Text = "Form1";
this.ResumeLayo ut(false);
}
private Button throwUI;
private Button throwNonUI;
}
public class Program
{
[STAThread]
static void Main()
{
Application.Thr eadException += delegate(object sender,
ThreadException EventArgs e)
{
string errorMsg = String.Format(" {0}", e.Exception.Mes sage);
MessageBox.Show (errorMsg, "Unhandled exception",
MessageBoxButto ns.OK,
MessageBoxIcon. Stop);
};
// Ignore configuration file settings - always route to
application handler.
Application.Set UnhandledExcept ionMode(Unhandl edExceptionMode .CatchException );
AppDomain.Curre ntDomain.Unhand ledException += delegate(object
sender, UnhandledExcept ionEventArgs e)
{
string errorMsg = String.Format(" {0} - IsTerminating = {1}",
e.ExceptionObje ct.ToString(), e.IsTerminating );
MessageBox.Show (errorMsg, "Unhandled exception",
MessageBoxButto ns.OK,
MessageBoxIcon. Stop);
};
Application.Ena bleVisualStyles ();
Application.Run (new Form1());
}
}
}
Willy.

"Chuck Cobb" <ch********@oxf ordcorp.com> wrote in message
news:uO******** ******@TK2MSFTN GP03.phx.gbl...
|I have an UhandledExcepti onEventHandler installed in the main thread, but
it
| doesn't seem to be picking up exceptions that originate in another thread.
| I've tried installing it in the other thread and it still doesn't seem to
be
| picking up the exception.
|
| "Willy Denoyette [MVP]" <wi************ *@telenet.be> wrote in message
| news:ep******** ******@TK2MSFTN GP04.phx.gbl...
| > ThreadException is meant to handle unhandled exceptions on the UI
thread,
| > you need to install an UnhandledExcept ionEventHandler to handle
unhandled
| > excptions on auxiliary threads.
| >
| > Willy.
| >
| > "Chuck Cobb" <ch********@oxf ordcorp.com> wrote in message
| > news:eT******** ******@TK2MSFTN GP04.phx.gbl...
| > | I'm implementing a centralized exception handling routine using the
| > | Enterprise Library Exception Management Application Block.
| > |
| > | I trap all unhandled exceptions to one place using the following
method:
| > |
| > | // --- Create an Exception Handler for Thread
| > Exceptions ----------------
| > |
| > | Application.Thr eadException += new
| > | ThreadException EventHandler(On ThreadException );
| > |
| > | // --- Create an Exception Handler for Unhandled
| > Exceptions -------------
| > |
| > | AppDomain currentDomain = AppDomain.Curre ntDomain;
| > |
| > | currentDomain.U nhandledExcepti on += new
| > | UnhandledExcept ionEventHandler (OnUnhandledExc eption);
| > |
| > |
| > |
| > | private static void OnThreadExcepti on(object sender,
| > |
| > | ThreadException EventArgs t)
| > |
| > | //
| > |
| >
*************** *************** *************** *************** *************** ***
| > |
| > | // Handles Normal Thread Exceptions
| > |
| > | //
| > |
| >
*************** *************** *************** *************** *************** ***
| > |
| > | {
| > |
| > | Exceptions.LogA ndReportError(t .Exception);
| > |
| > | }
| > |
| > |
| > |
| > | private static void OnUnhandledExce ption(object sender,
| > |
| > | UnhandledExcept ionEventArgs args)
| > |
| > | //
| > |
| >
*************** *************** *************** *************** *************** ***
| > |
| > | // Handles All Unhandled Exceptions
| > |
| > | //
| > |
| >
*************** *************** *************** *************** *************** ***
| > |
| > | {
| > |
| > | Exceptions.LogA ndReportError(a rgs.ExceptionOb ject as
System.Exceptio n);
| > |
| > | }
| > |
| > | The problem I have is that exceptions that occur on a background
thread
| > are
| > | not being picked up. If I do a "throw" on an exception in a
background
| > | thread it has no place to go and just disappears as an unhandled
| > exception.
| > | How can I pick up these exceptions without handling them in the
| > background
| > | thread?
| > |
| > | Thanks,
| > |
| > | Chuck Cobb
| > |
| > |
| >
| >
|
|

[Chuck Cobb]

Thanks for posting this code I tried it out and the primary difference
between your code and my code is how it starts an auxiliary thread:

Your code:
new Thread(delegate ()

{

ThrowExceptionI nsideTryCatch() ;

}).Start();

My Code:

MethodInvoker mi = new MethodInvoker(T hrowExceptionOu tsideTryCatch);

mi.BeginInvoke( null, null);

If I start an auxiliary thread using your method, it correctly catches the
exception from the auxiliary thread. If I start it my way, it doesn't work.
I have no idea why it should be different.

"Willy Denoyette [MVP]" <wi************ *@telenet.be> wrote in message
news:uD******** ******@TK2MSFTN GP05.phx.gbl...

Don't know what could be wrong with your code, but herewith a complete
sample that may set you on the right track.

using System;
using System.Diagnost ics;
using System.Componen tModel;
using System.Threadin g;
using System.Windows. Forms;
namespace Whatever
{
public class Form1 : Form
{
public Form1()
{
InitializeCompo nent();
}
private void throwUI_Click(o bject sender, EventArgs e)
{
throw new Exception("Thro wn from UI thread");
}
private void throwNonUI_Clic k(object sender, EventArgs e)
{
new Thread(delegate ()
{
throw new Exception("Thro wn from Aux thread");
}).Start();
}
private System.Componen tModel.IContain er components = null;
protected override void Dispose(bool disposing)
{
if (disposing && (components != null))
{
components.Disp ose();
}
base.Dispose(di sposing);
}
private void InitializeCompo nent()
{
this.throwUI = new Button();
this.throwNonUI = new Button();
this.SuspendLay out();

this.throwUI.Lo cation = new System.Drawing. Point(12, 12);
this.throwUI.Na me = "throwUI";
this.throwUI.Si ze = new System.Drawing. Size(95, 23);
this.throwUI.Ta bIndex = 0;
this.throwUI.Te xt = "Throw on UI";
this.throwUI.Cl ick += new
System.EventHan dler(this.throw UI_Click);

this.throwNonUI .Location = new System.Drawing. Point(12, 42);
this.throwNonUI .Name = "throwUI";
this.throwNonUI .Size = new System.Drawing. Size(95, 23);
this.throwNonUI .TabIndex = 0;
this.throwNonUI .Text = "Throw on non UI";
this.throwNonUI .Click += new
System.EventHan dler(this.throw NonUI_Click);

this.AutoScaleD imensions = new System.Drawing. SizeF(6F, 13F);
this.AutoScaleM ode = System.Windows. Forms.AutoScale Mode.Font;
this.ClientSize = new System.Drawing. Size(283, 150);

this.Controls.A dd(this.throwUI );
this.Controls.A dd(this.throwNo nUI);
this.Name = "Form1";
this.Text = "Form1";
this.ResumeLayo ut(false);
}
private Button throwUI;
private Button throwNonUI;
}
public class Program
{
[STAThread]
static void Main()
{
Application.Thr eadException += delegate(object sender,
ThreadException EventArgs e)
{
string errorMsg = String.Format(" {0}", e.Exception.Mes sage);
MessageBox.Show (errorMsg, "Unhandled exception",
MessageBoxButto ns.OK,
MessageBoxIcon. Stop);
};
// Ignore configuration file settings - always route to
application handler.

Application.Set UnhandledExcept ionMode(Unhandl edExceptionMode .CatchException );
AppDomain.Curre ntDomain.Unhand ledException += delegate(object
sender, UnhandledExcept ionEventArgs e)
{
string errorMsg = String.Format(" {0} - IsTerminating = {1}",
e.ExceptionObje ct.ToString(), e.IsTerminating );
MessageBox.Show (errorMsg, "Unhandled exception",
MessageBoxButto ns.OK,
MessageBoxIcon. Stop);
};
Application.Ena bleVisualStyles ();
Application.Run (new Form1());
}
}
}
Willy.

"Chuck Cobb" <ch********@oxf ordcorp.com> wrote in message
news:uO******** ******@TK2MSFTN GP03.phx.gbl...
|I have an UhandledExcepti onEventHandler installed in the main thread, but
it
| doesn't seem to be picking up exceptions that originate in another
thread.
| I've tried installing it in the other thread and it still doesn't seem
to
be
| picking up the exception.
|
| "Willy Denoyette [MVP]" <wi************ *@telenet.be> wrote in message
| news:ep******** ******@TK2MSFTN GP04.phx.gbl...
| > ThreadException is meant to handle unhandled exceptions on the UI
thread,
| > you need to install an UnhandledExcept ionEventHandler to handle
unhandled
| > excptions on auxiliary threads.
| >
| > Willy.
| >
| > "Chuck Cobb" <ch********@oxf ordcorp.com> wrote in message
| > news:eT******** ******@TK2MSFTN GP04.phx.gbl...
| > | I'm implementing a centralized exception handling routine using the
| > | Enterprise Library Exception Management Application Block.
| > |
| > | I trap all unhandled exceptions to one place using the following
method:
| > |
| > | // --- Create an Exception Handler for Thread
| > Exceptions ----------------
| > |
| > | Application.Thr eadException += new
| > | ThreadException EventHandler(On ThreadException );
| > |
| > | // --- Create an Exception Handler for Unhandled
| > Exceptions -------------
| > |
| > | AppDomain currentDomain = AppDomain.Curre ntDomain;
| > |
| > | currentDomain.U nhandledExcepti on += new
| > | UnhandledExcept ionEventHandler (OnUnhandledExc eption);
| > |
| > |
| > |
| > | private static void OnThreadExcepti on(object sender,
| > |
| > | ThreadException EventArgs t)
| > |
| > | //
| > |
| >
*************** *************** *************** *************** *************** ***
| > |
| > | // Handles Normal Thread Exceptions
| > |
| > | //
| > |
| >
*************** *************** *************** *************** *************** ***
| > |
| > | {
| > |
| > | Exceptions.LogA ndReportError(t .Exception);
| > |
| > | }
| > |
| > |
| > |
| > | private static void OnUnhandledExce ption(object sender,
| > |
| > | UnhandledExcept ionEventArgs args)
| > |
| > | //
| > |
| >
*************** *************** *************** *************** *************** ***
| > |
| > | // Handles All Unhandled Exceptions
| > |
| > | //
| > |
| >
*************** *************** *************** *************** *************** ***
| > |
| > | {
| > |
| > | Exceptions.LogA ndReportError(a rgs.ExceptionOb ject as
System.Exceptio n);
| > |
| > | }
| > |
| > | The problem I have is that exceptions that occur on a background
thread
| > are
| > | not being picked up. If I do a "throw" on an exception in a
background
| > | thread it has no place to go and just disappears as an unhandled
| > exception.
| > | How can I pick up these exceptions without handling them in the
| > background
| > | thread?
| > |
| > | Thanks,
| > |
| > | Chuck Cobb
| > |
| > |
| >
| >
|
|

[Willy Denoyette [MVP]]

"Chuck Cobb" <ch********@oxf ordcorp.com> wrote in message
news:%2******** ********@TK2MSF TNGP03.phx.gbl. ..
| Thanks for posting this code I tried it out and the primary difference
| between your code and my code is how it starts an auxiliary thread:
|
| Your code:
| new Thread(delegate ()
|
| {
|
| ThrowExceptionI nsideTryCatch() ;
|
| }).Start();
|
| My Code:
|
| MethodInvoker mi = new
MethodInvoker(T hrowExceptionOu tsideTryCatch);
|
| mi.BeginInvoke( null, null);
|

This doesn't start a auxiliary thread, it delegates the
ThrowExceptionO utsideTryCatch function to execute on the 'UI thread', but as
you call this from the UI thread, it simply boils down into a simple call to
ThrowExceptionO utsideTryCatch.

Willy.