Shimon Krokhmal's blog

couple weeks ago, my friend and co-worker, shani raba, presented me a problem.
they have some sealed application as an .exe file that throws some exceptions and crashes their application.

So, i Thought that is a good idea to wrap the targeted application with reflection, and catch the unhandled thrown exceptions.

to demonstrate this,
I've created an application with a button that throws an exception.

private void button1_Click(object sender, System.EventArgs e)
{
    throw new Exception("my Exception, need to be wrapped");
}

the next thing that we need to create is the wrapper.

so, creating a console application with this code should have solved the problem:

[STAThread]
static void Main(string[] args)
{

    Assembly assembly = Assembly.LoadFrom ("cashTester.exe");

    Type t = assembly.GetType("cashTester.Form1");
    object o = Activator.CreateInstance(t);
    try
    {
        Application.Run((Form)o);
    }
    catch(Exception ex)
    {
        Console.Write("exception was thrown : " + ex.Message);
    }
}

running this code in debug mode successfully catch the exception from the winform.
but, for some reason, in a normal run, this code won't catch the exception.

makes you wonder, huh ?

so i did some thinking, what on earth can make this phenomena ?
The answer is : Threads.
Yes, like it or not, but this is the subject that everyone tries to avoid it.
everyone knows it exists, and no one really likes it,
but we can't run from the problem, we need to confront it.

So, what can we do ?

since Application.Run launches a new thread, we can add to the Application.ThreadException event handler, an exception handling method.

like this class :

/// <summary>
/// The Wrapper class
/// </summary>
public class Wrapper
{

    /// <summary>
    /// Public cunstructor
    /// </summary>
    public Wrapper()
    {
    }

    /// <summary>
    /// This function will initialize the exception handling
    /// </summary>
    public void Init()
    {
        // define handlers for unhandled exceptions
        AppDomain.CurrentDomain.UnhandledException += new UnhandledExceptionEventHandler(this.exp);
        Application.ThreadException +=new System.Threading.ThreadExceptionEventHandler(this.ThreadExp);
    }

    /// <summary>
    /// This method is for the threads exceptions
    /// </summary>
    /// <param name="o">the object</param>
    /// <param name="args">Thread exception args</param>
    void ThreadExp(object o, System.Threading.ThreadExceptionEventArgs args)
    {
        // Write the message to the console
        Console.Write("Unhandled thread exception was thrown : " + args.Exception.Message);
    }

    /// <summary>
    /// This method is for the unhandled exceptions from the main thread
    /// </summary>
    /// <param name="o">the object</param>
    /// <param name="args">exception arguments</param>
    void exp(object o,System.UnhandledExceptionEventArgs args)
    {
        // Write the message to the console
        Console.Write("Unhandled exception was thrown : " + ((Exception)args.ExceptionObject).Message);
    }

    public void Run()
    {
        // Load the assembly
        Assembly assembly = Assembly.LoadFrom ("cashTester.exe");

        // get the type of the object
        Type t = assembly.GetType("cashTester.Form1");

        // invoke it
        object o = Activator.CreateInstance(t);

        // Run the application - note that this line starts an additional thread
        Application.Run((Form)o);
    }
}

now, all we need is to launch it :

/// <summary>
/// The main entry point for the application.
/// </summary>
[STAThread]
static void Main(string[] args)
{
    Wrapper w = new Wrapper();
    w.Init();
    w.Run();
}

now we got an exception wrapper for launching applications.

Shani, tell me if that helped ...

p.s.
There are more ways to do it, but this is the simplest one

the main reason that I've started to play with threads is because the industry WILL (sooner or later) move to a multi-core guided programing, and it WILL become mainstream (mark my words :) ).

any way, lets start from the beginning, and why do we need threads.
according to the definition : "Threads are a way for a program to split itself into two or more simultaneously (or pseudo-simultaneously) running tasks. Threads and processes differ from one operating system to another, but in general, the way that a thread is created and shares its resources is different from the way a process does."

so, in other words, we will use threads when we need to perform simultaneous tasks.
these kind of actions made when you have unused processing time while waiting for other task to finish.

so, back to the .Net world, how would we do that ?

to use threads, we need to include the library :

the next thing we need i to know how to to lunch a thread with a task.

• we need to create a task to be done.
• a ThredStart delegate which will point to our task.
• a new thread ( or an old one from a thread pool ) - which is better and when will be explained in some later posts.
• start the thread.

so :

lets create some task :

        private void BurnCPUwithOneThread()
        {
            for(int i=0; i< 5000000;i++)
            {
                lblcounter.Text = i.ToString();
            }
        }

and one more :

        private void BurnCPUwithTwoThreads()
        {
            for(int i=0; i< 5000000;i++)
            {
                lblCounter2.Text = i.ToString();
            }
        }

now we will create the delegate and the threads, and activate them.

While surfing the net for some new hardware tech toys, i encountered an article about multi-core guided software architecture.

"Intel's support in multi-core education is critical for two reasons," said Karsten Schwan, professor of College of Computing, Georgia Institute of Technology. "First, getting early access to advanced technology and new equipment is something that always excites students. Second, companies like Intel have a perspective that looks beyond research to see the broader potential for technology."

For us, it means changing the whole perception of software architecture, design and implementation such as parallelism, threading concepts, threading methodology and programming with threads