Plugin architecture and event handlers

[Anton Zinchenko]

I'm trying to write some kind of plugin framework... It looks something like this:
Host Application (Windows Form Application) loads plugins into separate AppDomains (each plugin into own AppDomain).
How to set a method from plugin as eventhandler for MenuItem Click event (MenuStrip is on the main form of host application) and prevent loading plugin assembly into the main AppDomain?

[Anton Zinchenko]

I'm still has no luck with this question...

Host application:

    public partial class Form1 : Form
    {
        private AssemblyLoader _aLoader = null;

        public Form1()
        {
            InitializeComponent();

            AppDomain _domain = AppDomain.CreateDomain("Remote Load");
            _aLoader = (AssemblyLoader)_domain.CreateInstanceAndUnwrap(
                                     "Loader", "Loader.AssemblyLoader");

            _aLoader.Load();

            EventHandler eh = (EventHandler)Delegate.CreateDelegate(typeof(EventHandler), _aLoader.Instance, _aLoader.Method);

            button1.Click += eh;
        }
    }

AssemblyLoader:

    [Serializable]
    public class AssemblyLoader : MarshalByRefObject
    {
        object _instance = null;
        MethodInfo _method = null;

        public void Load()
        {
            Assembly _assembly = Assembly.LoadFile(Environment.CurrentDirectory + @"\Plugin.dll");
            Type _type = _assembly.GetType("Plugin.Test");
            _instance = Activator.CreateInstance(_type);
            _method = _instance.GetType().GetMethod("TestEventHandler");
        }

        public MethodInfo Method
        {
            get { return _method; }
        }

        public object Instance
        {
            get { return _instance; }
        }
    }

Plugin:

    [Serializable]
    public class Test
    {
        public void TestEventHandler(object sender, System.EventArgs e)
        {
            MessageBox.Show("Pingback from plugin");
        }      
    }

In this case button click causes plugin.dll to load into the main appdomain... =(
Any suggestions how to prevent this?