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Feature addiction

Friday, April 29, 2005
Fun
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Funny how quickly you get used to new features. Looking at a map on a web site, I found myself trying to drag the map with the mouse, à la Google Maps...
Conclusion: even if at first sight some features may look like gadgets, your mind can get addicted to them anyway and they become key differentiating features.

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Hosted source control

Wednesday, April 27, 2005
Sites Tools
5 Comments

In case you need to host your code online, mostly for open source projects, here are some providers you can try:
- http://www.tigris.org (Subversion and CVS)
- http://developer.berlios.de (Subversion and CVS)
- http://wdevs.com (Vault)
- http://freepository.com (CVS)
- http://sourceforge.net (Subversion and CVS, often reported as slow)
- http://sunsite.dk
- http://community.java.net/projects (for Java project obviously)
- http://www.sourcehosting.net (CVS, not free)
- http://www.projxpert.com (Subversion)
- http://wush.net (Subversion, not free)
- http://www.cvsdude.org (Subversion and CVS)
- http://www.projectlocker.com (Subversion and CVS, not free)
- http://www.bitkeeper.com/Hosted.html (BitKeeper)
- http://forge.novell.com (Subversion and CVS)
- https://opensvn.csie.org (Subversion)
- http://www.hosted-projects.com (Subversion)
- http://www.codeplex.com (Visual Studio Team Foundation Server, Subversion)
- http://www.devguard.com (Subversion, not free)
- http://www.assembla.com (Subversion)
- http://www.orcsweb.com/hosting/sourcegearvault.aspx (Vault, not free)
- http://www.dynamsoft.com/Products/SAWhosted_Overview.aspx (SourceAnywhere)
- http://www.codespaces.com (Subversion)
- http://svnrepository.com (Subversion, not free)
- http://sharpforge.org and http://sharpforge.com (Subversion)
- http://www.projecthut.com (Subversion, not free)
- http://xp-dev.com (Subversion)
- http://sliksvn.com (Subversion)
- http://code.google.com/projecthosting (Subversion)
- http://www.scmsoftwareconfigurationmanagement.com (SCM Anywhere)
- http://www.scmsoftwareconfigurationmanagement.com (SourceAnywhere)
- http://www.a2hosting.com (Subversion and CVS, not free)
- http://beanstalkapp.com (Subversion)
Notes:
- Not all accept closed source projects.
- Not all support binary releases.
- Most offer more services than just source code hosting: forums, bug tracking, task management, project web site, etc.
Page sponsored by A2 Hosting

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How to handle unhandled exceptions in Windows Forms

Thursday, April 21, 2005

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If you've already handled unhandled exceptions in your Windows Forms applications, your probably know the Application.ThreadException event. Thanks to this event, all you have to do is to:

Register a handler for the event
Handle the exception in this event handler

Here is an example:

[STAThread]
static void Main()
{
  Application.ThreadException += new ThreadExceptionEventHandler(Application_ThreadException);
  Application.Run(new FrmMain());
}

private static void Application_ThreadException(object sender, ThreadExceptionEventArgs e)
{
  MessageBox.Show("Unhandled exception: "+e.Exception.ToString());
}

If you want to reuse the default dialog box, you can use the following code:

if (SystemInformation.UserInteractive)
{
  using (ThreadExceptionDialog dialog = new ThreadExceptionDialog(exception))
  {
    if (dialog.ShowDialog() == DialogResult.Cancel)
      return;
  }
  Application.Exit();
  Environment.Exit(0);
}

This is all fine and easy, but what if you have several threads? What if an exception is thrown in a thread other than the main one?
Well, the answer is simple: you won't be notified by the Application.ThreadException event.
Of course there is a solution: you can use the AppDomain.UnhandledException event instead. There is one thing to be aware of though: your event handler will be executed by the thread that threw the exception. This can be a problem if you want to display something or interact with graphical components, because all this kind of actions should be performed in the same thread (the main thread).

Here is a code sample that shows a complete solution that takes care of this:

private delegate void ExceptionDelegate(Exception x);

static private FrmMain _MainForm;

/// <summary>
/// The main entry point for the application.
/// </summary>
[STAThread]
static void Main()
{
  _MainForm = new FrmMain();
  AppDomain.CurrentDomain.UnhandledException += new UnhandledExceptionEventHandler(AppDomain_UnhandledException);
  Application.Run(_MainForm);
}

private static void AppDomain_UnhandledException(object sender, UnhandledExceptionEventArgs e)
{
  Exception exception;

  exception = e.ExceptionObject as Exception;
  if (exception == null)
 {
 // this is an unmanaged exception, you may want to handle it differently
    return;
 }
  PublishOnMainThread(exception);
}

private static void PublishOnMainThread(Exception exception)
{
  if (_MainForm.InvokeRequired)
  {
    // Invoke executes a delegate on the thread that owns _MainForms's underlying window handle.
    _MainForm.Invoke(new ExceptionDelegate(HandleException), new object[] {exception});
  }
  else
  {
    HandleException(exception);
  }
}

private static void HandleException(Exception exception)
{
  if (SystemInformation.UserInteractive)
  {
    using (ThreadExceptionDialog dialog = new ThreadExceptionDialog(exception))
    {
      if (dialog.ShowDialog() == DialogResult.Cancel)
        return;
    }
    Application.Exit();
    Environment.Exit(0);
  }
}

private void ThreadMethod()
{
  throw new Exception("From new thread");
}

private void button1_Click(object sender, System.EventArgs e)
{
  Thread thread;
  thread = new Thread(new ThreadStart(ThreadMethod));
  thread.Start();
}

Nota Bene: You'll have to register a handler for the UnhandledException event for each AppDomain.
Nota Bene 2: The UnhandledExceptionEventArgs parameter contains a IsTerminating property that indicates whether the common language runtime is terminating. Something to test in order to know what to do with the exception.

Thanks to Pierrick for the help.

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Feature addiction

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How to handle unhandled exceptions in Windows Forms

How to handle unhandled exceptions in Windows Forms

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