How do I continue running after an unhandled exception?

Question

I have the following code in my application that is running after an unhandled exception:

AppDomain.CurrentDomain.UnhandledException += new UnhandledExceptionEventHandler(CurrentDomain_UnhandledException);

static void CurrentDomain_UnhandledException(object sender, UnhandledExceptionEventArgs e)
        {
            var exception = e.ExceptionObject as Exception;
            if (exception != null) MessageBox.Show(exception.Message + " - " + exception.StackTrace);
        }

but even if i catch unhandled exception my windows mobile application close. How to prevent closing application when i catch unhandled exception. I never want to close my app. I want to open Login form in this scenario or anything else not close app.

So what i want is to prevent closing application from unhandled exception like network is down,...

I can not use try catch in every code ....

Any idea how to prevent closing app when network is down or any other unhandled exceptions?

Answer 1

You don't. When you get an AppDomain unhandled exception, your app is no longer in a stable state. Where exactly would you resume to? When you've gotten to that point, your only option, with good reason, is to exit. You could reasonably schedule yourself to run again to make sure the app comes back, but a far better idea is to actually handle the exception at its source and prevent it from being an UnhandledException.

Answer 2

In your app.config add the following element

<runtime>
  <!-- the following setting prevents the host from closing when an unhandled exception is thrown -->
  <legacyUnhandledExceptionPolicy enabled="1" />
</runtime>

Answer 3

You can, and you should use try...catch and handle the exceptions in every situation where an exception might occur. (In languages like Java you can't even compile your code until you catch every exception that the called function might throw or declare explicitly that this particular function won't catch it, so the one that calls it should do it.)

If you want to minimize the cases where you use try...catch some bad situations can be prevented with testing if the necessary conditions are met so you won't even call a function that is known for throwing a particular exception. Like calling

if (myByteArray != null)
{
    myIPAddress = new IPAddress(myByteArray);
}

because this way the IPAddress constructor won't throw an ArgumentNullException.

However in most of the cases this can't be done, especially with networking, because you can't predict if the cable will be cut, the signal will be lost, the database server will crush, etc. in the middle of the transaction. So you should try...catch every time you connect to the network or send data to or receive data from a connection.

Answer 4

AppDomain.CurrentDomain.UnhandledException fires on any unhandled exception on any thread, but since CLR 2.0, the CLR forces application shutdown after your event handler completes. However, you can prevent shutdown by adding the following to your application configuration file:

<configuration>
  <runtime>
    <legacyUnhandledExceptionPolicy enabled="1" />
  </runtime>
</configuration>

Answer 5

I think you need to use Application.ThreadException When you subscribe to Application.ThreadException, unhandled exceptions wont hit the UnhandledException and the app will keep running.