How do I pass CancellationToken across AppDomain boundary?

Question

I have a command object, doing work based on a request from a request queue. This particular command will execute its work in a child appdomain. Part of doing its work in the ch

Answer 1

There is actually a much easier way to overcome this obstacle assuming your proxy type is a single responsibility. I am assuming of course that you maintain a collection of your created domains and unload them should your application be closed or your containing object be disposed. I also assume the reason you need the cancellation token is to cancel some async operation in your marshaled reference type. You simply need to do the following:

Create your tokenSource and token fields and initialize them in your constructor.

_cancellationTokenSource = new CancellationTokenSource();
_token = _cancellationTokenSource.Token;

Subscribe to the following events. The UnhandledException will serve the purpose of catching any faulting exception which causes your domain to close prematurely. This should be a best practice.

var currDomain = AppDomain.CurrentDomain;
            currDomain.DomainUnload += currDomain_DomainUnload;
            currDomain.UnhandledException += currDomain_UnhandledException;

Call cancel on your token source when the domain unload event is called. Additionally you may want to have a dispose method that unsubscribes to the domain events that gets called from either or just let the domain cleanup process garbage collection.

void currDomain_DomainUnload(object sender, EventArgs e)
    {
        _log.Debug(FormatLogMessage(_identity, "Domain unloading Event!"));
        _cancellationTokenSource.Cancel();
        _logPlayer.Dispose();
    }

 void currDomain_UnhandledException(object sender, UnhandledExceptionEventArgs e)
    {
        _log.Error(string.Format("***APP Domain UHE*** Error:{0}", e.ExceptionObject);
        _cancellationTokenSource.Cancel();
        _logPlayer.Dispose();
    }