Not Loading Rhino Plugin at Startup

Rhino Developer
3

That looks like the perfect approach, however the method Rhino.UI.Panels.ClosePanel() doesn’t seem to do anything. The plugin is still there when I restart Rhino and when I debug it step by step I don’t see any changes either.

public class MyRhinocerosPlugIn : Rhino.PlugIns.PlugIn
 {

        public MyRhinocerosPlugIn()
        {
            Instance = this;
            RhinoDoc.CloseDocument += close_plugin;
        }

        protected void close_plugin (object sender, DocumentEventArgs e) 
        {
            // This does nothing
            Rhino.UI.Panels.ClosePanel(typeof(MyPanelHost));

            // This returns a guid, but it does nothing
            var my_guid = typeof(MyPanelHost).GUID;
            Rhino.UI.Panels.ClosePanel(my_guid);

            // This returns null
            var my_panel = Rhino.UI.Panels.GetPanel<MyPanelHost>();

            // this returns the guids of the panels, but then all the items of panel_list are null
            var guids = Rhino.UI.Panels.GetOpenPanelIds();
            var panel_list = new List<object>();
            foreach (var guid in guids)
            {
                var panel = Rhino.UI.Panels.GetPanel(guid);
                panel_list.Add(panel);
            }            
          
            // this throws an error, because RhinoDoc.ActiveDoc is null
            var my_panel2 = Rhino.UI.Panels.GetPanel<MyPanelHost>(RhinoDoc.ActiveDoc);
        }
}

I also read that the plugins started from c++ are not accessible through these methods. May it be the case? Although my plugin is a .NET assembly.