Why no error message from the exception ?

[5883]

Hi All,

i have a code like this,

try
{
// some code here
...
Thread.Sleep(1000);
}
catch(Exception e)
{
MessageBox.Show(e.ToString());

if (mainDemoForm.stopWorkerThread == false)
{
MessageBox.Show("Error occured in Windows shared memory utility thread");
}
return;
}

My question is, i can see the message box saying "Error occured in ...",
but i cannot see the 1st message box, why ?

[5883]

BTW, this VS 2008, .net 3.5 sp1

[someuser77]

Hello 5883,
Is the behavior you described consistent or are there occasions when you do see the exception message box?
Can you post a working part of the code that reproduces the issue?
If so I advise you to use the code tags '[ code]' and '[/code]'.

[Arjay]

Hi All,

i have a code like this,

try
{
// some code here
...
Thread.Sleep(1000);
}
catch(Exception e)
{
MessageBox.Show(e.ToString());

if (mainDemoForm.stopWorkerThread == false)
{
MessageBox.Show("Error occured in Windows shared memory utility thread");
}
return;
}

My question is, i can see the message box saying "Error occured in ...",
but i cannot see the 1st message box, why ?

Are you creating a second thread?

[5883]

yes, it's consistent.
i'll try more tomorrow, if still no good, will try to post a sample c# file.

Hello 5883,
Is the behavior you described consistent or are there occasions when you do see the exception message box?
Can you post a working part of the code that reproduces the issue?
If so I advise you to use the code tags '[ code]' and '[/code]'.

[5883]

Are you creating a second thread?

there're threads, but for this function, not creating thread. Actually if i simplify the code, it still the same result

            do
            {

                try
                {
                    Thread.Sleep(1000);
                }
                catch(Exception e)
                {
                    MessageBox.Show(e.ToString());

                    if (mainDemoForm.stopWorkerThread == false)
                    {
                        MessageBox.Show("Error occured in Windows shared memory utility thread");
                    }
                    return;
                }

            } while (mainDemoForm.stopWorkerThread == false);

[Arjay]

there're threads, but for this function, not creating thread.

The code you posted isn't causing the error.

I can mock up the MainDemoForm class and run the code in a console app and it will run forever. I can even lower the Sleep to 0 or get rid of it and the program still won't crash (but it will burn up the cpu cycles).

namespace ConsoleApplication3
{
    class MainDemoForm
    {
        public bool StopWorkerThread { get; set; }   
    }
    class Program
    {
        static void Main( string [ ] args )
        {
            var mainDemoForm = new MainDemoForm( );

            do
            {

                try
                {
                    Thread.Sleep( 0 );
                }
                catch ( Exception e )
                {
                    MessageBox.Show( e.ToString( ) );
                    
                    if ( mainDemoForm.StopWorkerThread == false )
                    {
                        MessageBox.Show( "Error occured in Windows shared memory utility thread" );
                    }
                    return;
                }

            } while ( mainDemoForm.StopWorkerThread == false );
        }
    }
}

What I'm trying to tell you is that the problem isn't in the code snippet that you given - it's else where. Perhaps, you have an issue with the threading, have a race condition or are corrupting the stack. Btw, if this code is running inside a worker thread, you shouldn't be access any UI components - UI components should only be accessed from the primary UI thread.

[5883]

Hi Arjay,

my guess is the somewhere else as well, we have the GUI thread spawns 2 worker threads.
Based on the button we click in the GUI, we set the flags and control the 2 worker threads.
Here mainDemoForm.StopWorkerThread is one of the flags.
So i'm kind of surprised to see your comment
"if this code is running inside a worker thread, you shouldn't be access any UI components"
what should be the correct way then ?

on the other hand, still i'm confused why exception happened in this code, not the code really causing the issue.

thanks !

The code you posted isn't causing the error.

I can mock up the MainDemoForm class and run the code in a console app and it will run forever. I can even lower the Sleep to 0 or get rid of it and the program still won't crash (but it will burn up the cpu cycles).

namespace ConsoleApplication3
{
    class MainDemoForm
    {
        public bool StopWorkerThread { get; set; }   
    }
    class Program
    {
        static void Main( string [ ] args )
        {
            var mainDemoForm = new MainDemoForm( );

            do
            {

                try
                {
                    Thread.Sleep( 0 );
                }
                catch ( Exception e )
                {
                    MessageBox.Show( e.ToString( ) );
                    
                    if ( mainDemoForm.StopWorkerThread == false )
                    {
                        MessageBox.Show( "Error occured in Windows shared memory utility thread" );
                    }
                    return;
                }

            } while ( mainDemoForm.StopWorkerThread == false );
        }
    }
}

What I'm trying to tell you is that the problem isn't in the code snippet that you given - it's else where. Perhaps, you have an issue with the threading, have a race condition or are corrupting the stack. Btw, if this code is running inside a worker thread, you shouldn't be access any UI components - UI components should only be accessed from the primary UI thread.

[TheGreatCthulhu]

There's something I don't get. The OP said:

My question is, i can see the message box saying "Error occured in ...",
but i cannot see the 1st message box, why ?

And this is the code originally posted - the message box referred to earlier is in a bold blue font:

try
{
    // some code here 
    // ...
    Thread.Sleep(1000);
}
catch(Exception e)
{
    MessageBox.Show(e.ToString());

    if (mainDemoForm.stopWorkerThread == false)
    {
        MessageBox.Show("Error occured in Windows shared memory utility thread");
    }
    return;
}

How come that line is executed, when the catch block is never reached?
5883, are you sure there are no other pieces of code that could have caused a similar message box to appear? A simple way to test is to alter the text and see if it has an effect.

This would mean not only that Arjay is right about the code not causing the error, but also that the error-handling code showing the message box is not the one that is posted here.

[5883]

well, we did double check, this is the only place.
guess i'm still new to c# and not quite understand some of the behaviors.

There's something I don't get. The OP said:


And this is the code originally posted - the message box referred to earlier is in a bold blue font:

try
{
    // some code here 
    // ...
    Thread.Sleep(1000);
}
catch(Exception e)
{
    MessageBox.Show(e.ToString());

    if (mainDemoForm.stopWorkerThread == false)
    {
        MessageBox.Show("Error occured in Windows shared memory utility thread");
    }
    return;
}

How come that line is executed, when the catch block is never reached?
5883, are you sure there are no other pieces of code that could have caused a similar message box to appear? A simple way to test is to alter the text and see if it has an effect.

This would mean not only that Arjay is right about the code not causing the error, but also that the error-handling code showing the message box is not the one that is posted here.

[Arjay]

Comment out the code that creates the threads and the shared memory.

Then add the code back in until the problem repros.