Subscribe to DomainUnload event from a main AppDomain

Question

I'm creating an application which works with a new AppDomain that can be created and unloaded. I'd like to handle the DomainUnload event so I need to subscribe to it. I can't subscribe to this event from the new AppDomain that can be unloaded as all members from there will not be accessible once the domain is unloaded.

But when I try to subscribe to this event from Main AppDomain I always getting the exception: " System.Runtime.Serialization.SerializationException: Type 'MyNamespace.MainWindow' in assembly 'MyMainAssembly' is not marked as serializable. "

Initially I tried to add an attribute [Serializable] to class in the main app domain, but it didn't help. Then I created a new class 'RemoteHandlerClass' derived from MarshalByRefObject and put the subscription code in it, but I'm also getting the same error. Using the [Serializable] attribute in this class also didn't help. To access members from this class I use proxy object in main app domain created by:

var remoteHandler = (RemoteHandlerClass)workerDomain.CreateInstanceAndUnwrap(
    typeof(RemoteHandlerClass).Assembly.FullName, typeof(RemoteHandlerClass).FullName);

How can I subscribe to this event? Preferably I would like to subscribe to this event from the main app domain. The code below can reproduce my issue.

Thanks!

public partial class MainWindow : Window
{
    private void Button_Click(object sender, RoutedEventArgs e)
    {
        var newDomain = AppDomain.CreateDomain("New domain");
        newDomain.DomainUnload += UnloadHandler; // System.Runtime.Serialization.SerializationException:
                                                 // Type 'MyNamespace.MainWindow' in assembly 'MyMainAssembly'
                                                 // is not marked as serializable.
    }
    
    private void UnloadHandler(object sender, EventArgs e)
    {
        
    }
}

Answer 1

So, when dealing with AppDomains, your handler object needs to be MarshalByRefObject which its not -- it's just a Window type. Wrap what you are doing in a simple class such as

class DomainContainer : MarshalByRefObject
    {
        public void StartDomain()
        {
            var newDomain = AppDomain.CreateDomain("New domain");
            newDomain.DomainUnload += UnloadHandler;
            
        }

        private void UnloadHandler(object sender, EventArgs e)
        {

        }
    }

and call that in your app.

 private void Button_Click(object sender, RoutedEventArgs e)
        {
            var d = new DomainContainer();
            d.StartDomain();
        }