How to catch unhandled exceptions thrown in AutoCAD.NET

Question

In my Autocad.NET app I want to log all unhandled exceptions using log4net. AutoCAD itself shows an error dialog with a detailed message -> so there must be a way to register to a certain event.

I tried to register the AppDomain.CurrentDomain.UnhandledException event at app initialization:

AppDomain.CurrentDomain.UnhandledException += (s, e) =>
{
     System.Exception exception = (System.Exception)e.ExceptionObject;
     log.Error(String.Format("Unhandled Exception: {0}\n{1}", exception.Message, exception.StackTrace));
};

But this event is never fired.

Answer 1

In ObjectARX, there is a function called acedDisableDefaultARXExceptionHandler. You can try to P/Invoke it.

    // EntryPoint may vary across autocad versions
    [DllImport("acad.exe", EntryPoint = "?acedDisableDefaultARXExceptionHandler@@YAXH@Z")]
    public static extern void acedDisableDefaultARXExceptionHandler(int value);

You can also try System.Windows.Forms.Application.ThreadException: http://through-the-interface.typepad.com/through_the_interface/2008/08/catching-except.html

The simplest way to do this is to wrap all your code in a try/catch block. In AutoCAD, there is 2 ways to execute code :

With a command

To avoid duplicate code, declare an interface like this:

public interface ICommand
{
  void Execute();
}

Then use it for your command:

public class MyCommand : ICommand
{
  void Execute()
  {
    // Do your stuff here
  }
}

In the class where your commands are defined, use this generic method to execute :

void ExecuteCommand<T>() where T : ICommand
{
  try
  {
    var cmd = Activator.CreateInstance<T>();
    cmd.Execute();
  }
  catch (Exception ex)
  {
    Log(ex);
  }
}

Now your command looks like this:

[CommandMethod("MYCMD", CommandFlags.Modal)]
public void MyCommand()
{
  ExecuteCommand<MyCommand>();
}

In an event handler

In this case, as you need the event arguments, simply wrap your code in the try/catch directly.