How to avoid multiple messageboxes continuous display?

Question

I have a problem with WPF MessageBox,its due to when internet connection is not available. I need the message to displays once only, but it shows multiple times.

 private void Application_Startup(object sender, StartupEventArgs e)
    {
        AppDomain.CurrentDomain.UnhandledException += new UnhandledExceptionEventHandler(cc);
    }
    void cc(object sender, UnhandledExceptionEventArgs e)
    {
        Exception ex = e.ExceptionObject as Exception;
        MessageBox.Show(ex.Message, "Uncaught", MessageBoxButton.OK);
    }

Answer 1

Simple.
You should confirm before you show message box.

// message box flag.
bool canIShowMessageBox = true;

// for thread lock.
object exLocker = new object();    

void cc(object sender, UnhandledExceptionEventArgs e)
{
   lock(exLocker)
   {
      if (canIShowMessageBox)
         canIShowMessageBox = false;
      else
         return;
   }
   Exception ex = e.ExceptionObject as Exception;
   MessageBox.Show(ex.Message, "Uncaught", MessageBoxButton.OK);

   lock(exLocker)
      canIShowMessageBox = true;
}