uncaught exception handlers

[George_George]

No, N a v a n e e t h. Not catch all exceptions, you can not catch exception from other threads? Right? regards, George

[George_George]

Thanks PIEBALDconsult, Good reference. :-) regards, George

[George_George]

Thanks Derek, What do you mean "didn't specify 'massive' which didn't help" and "relative to performing an if test to prevent the exception"? Could you show more description or some pseudo code about your approach please? regards, George

[N a v a n e e t h]

George_George wrote:

you can not catch exception from other threads? Right?

Yes. You are right. I missed that. Hook AppDomain.UnhandledException which handles all exception other than the ones I specified in my first message.

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[George_George]

You mean "Also exceptions occurring in unmanaged resources won't be handled too" will not be handled? regards, George

[MidwestLimey]

Derek Bartram wrote:

Does anyone know if a try...catch block affects the performance of the try block code? I know it has a performance hit on hitting the block, but I wonder if it has a continuing effect beyond that.

I once worked on a project where the Project Lead insisted on try catch blocks in every bloody method. I did some performance testing and could determine definitive costs with the setup and teardown of the block, but was unable to measure any discernable difference to the code internally. However the code was entirely managed, perhaps wrapping unmanaged code has other implications.

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I'm largely language agnostic

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After a while they all bug me :doh:

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[Spacix One]

If you wanted to go that far you can catch errors in your thread method also... Are you looking for on error resume next type functionally? If so might be better to use VB.NET as C# doesn't allow for that coding horror :) You need to remember the following: Using exceptions to control programming logic is is the same as having car insurance to repair the damange after rolling off a cliff instead of setting the parking break to prevent it from rolling away.

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-Spacix All your skynet questions[^] belong to solved

[N a v a n e e t h]

George_George wrote:

"Also exceptions occurring in unmanaged resources won't be handled too"

Yes. It won't be handled. Because it runs out of CLR.

All C# applications should call Application.Quit(); in the beginning to avoid any .NET problems.- Unclyclopedia How to use google | Ask smart questions

[George_George]

Thanks Spacix, 1.

Spacix One wrote:

If you wanted to go that far you can catch errors in your thread method also...

So, no means to catch exception from another thread, right? :-) 2.

Spacix One wrote:

on error resume next type functionally? If so might be better to use VB.NET as C# doesn't allow for that coding horror

Sorry, I have no experience in VB. Could you say something alternative to describe your ideas please? I do not quite understand, especially what do you mean "on error resume next type functionally". :-) regards, George

[George_George]

Thanks N a v a n e e t h, 1. Seems UnhandledException is the only approach to handle exception from other threads, and I have tried even ProcessExit does not work. Here is my code to test. Could you review whether my code and my points are correct? :-) 2. After the handler for UnhandledException is executed, process is always terminated?

using System;
using System.Threading;

namespace DelegateThread
{
class Test
{
private static void Method2 (object input)
{
Console.WriteLine("Method1 is throwing exception");
throw new ApplicationException("**** oops ****");
}

    private static void Method1()
    {
        Console.WriteLine("Method1 is throwing exception");
        throw new ApplicationException("\*\*\*\* oops \*\*\*\*");
    }

    private static void Handler1 (object sender, EventArgs e)
    {
        Console.WriteLine ("I am here");
    }

    private static void Handler3(object sender, EventArgs e)
    {
        Console.WriteLine("I am here");
    }

    delegate void Method1Delegate();

    static void Main(string\[\] args)
    {
        Console.WriteLine("We first use a thread");

        AppDomain.CurrentDomain.ProcessExit += new EventHandler (Test.Handler1);
        AppDomain.CurrentDomain.UnhandledException +=new UnhandledExceptionEventHandler(Test.Handler3);
        
        Thread aThread
            = new Thread(new ThreadStart(Method1));
        aThread.Start();
        


        Thread.Sleep(5000);

        Console.WriteLine("Survived exception");

        return;

    } // main
}

}

regards, George

[George_George]

But you can never catch exception from other threads, PIEBALDconsult. :-) regards, George

[George_George]

What do you mean "unable to measure any discernable difference to the code internally"? regards, George

[N a v a n e e t h]

George_George wrote:

and I have tried even ProcessExit

ProcessExist is not needed here

George_George wrote:

After the handler for UnhandledException is executed, process is always terminated?

mm, look like you are still not clear. I will try to explain once more. AppDomain.UnhandledException is not an exception handler like catch. It's an event which will be fired before program exits due to uncaught error. After handler is executed, process will be terminated. This is a new behavior from .NET 2.0 onwards. In handler you can do necessary steps to log the error. You can't prevent application ending. In that handler you can show friendly messages to user and inform him that we are closing. Considering all these points in mind, your demo code is working as expected. Handler is getting executed and application is closing. You need to change the handler3() method like this.

private static void Handler3(object sender, UnhandledExceptionEventArgs e)
{
Exception exceptionOccured = e.ExceptionObject as Exception;
string errorMessage = exceptionOccured.Message;
Console.WriteLine("I am here");
}

. In this you can see how exception occurred is retrieved from the event argument. You can log the exception message and application will be exited gracefully. .NET 1.1 behavior can be taken back by setting some flag value in application.config file. See this[^]. But I don't recommend that, as I don't know the pros/cons of that. Hope it's clear now.

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[N a v a n e e t h]

George_George wrote:

I do not quite understand, especially what do you mean "on error resume next type functionally".

It's a VB syntax used to resume the processing on errors. If on error resume next is provided on the code, errors will be skipped. Keep it in mind, this is for VB/VB.NET and not for C#.

All C# applications should call Application.Quit(); in the beginning to avoid any .NET problems.- Unclyclopedia How to use google | Ask smart questions

[Spacix One]

N a v a n e e t h answered #2 As for number one you can catch them in that thread, example:

System.Threading.Thread mythread = new System.Threading.Thread
(delegate()
{
try
{
throw new Exception("Oh no, my thread crashed!");
}
catch(Exception err)
{
File.WriteAllText(Environment.GetFolderPath(Environment.SpecialFolder.Desktop) + @"\error.log",
DateTime.Now.ToString() + Environment.NewLine + err.ToString() + Environment.NewLine + Environment.NewLine);
}
});
mythread.Start();

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-Spacix All your skynet questions[^] belong to solved

[George_George]

Thanks N a v a n e e t h, Cool! I have made further tests that, there is one exception case. When exception is from thread pool thread -- but in the situation of executing asynchronous method call, we can catch the exception (even if unhandled in the thread pool worker thread) in EndInvoke in main thread. So, here is a case when there is unhandled exception in another thread, we can still catch it and not make process terminated. :-) Any comments? regards, George

[George_George]

Thanks for clarification, N a v a n e e t h! regards, George

[George_George]

Yes, Spacix! I agree with your code. I think the only case which we can catch exception other threads and prevent application process from termination is, http://www.codeproject.com/script/Forums/View.aspx?fid=1649&msg=2529071[^] Agree? Any comments? :-) regards, George

[MidwestLimey]

I couldn't find a time difference for the execution of the same code block when wrapped in a try catch as opposed to not.

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I'm largely language agnostic

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After a while they all bug me :doh:

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[George_George]

Thanks MidwestLimey, So you mean the performance impact of exception handling is minor? regards, George